Improve docs.

Fixes some REST formatting errors, improves language in several places,
and fixes some incorrect code examples.

docs/userguide/canvas.rst

@@ -151,7 +151,7 @@ Callbacks
 .. versionadded:: 3.0
 
 Callbacks can be added to any task using the ``link`` argument
-to ``apply_async``:
+to ``apply_async``::
 
     add.apply_async((2, 2), link=other_task.subtask())
 
@@ -232,7 +232,7 @@ The Primitives
 The primitives are also subtasks themselves, so that they can be combined
 in any number of ways to compose complex workflows.
 
-Here's some examples::
+Here's some examples:
 
 - Simple chain
 
@@ -478,13 +478,13 @@ you chain tasks together:
 
     # (4 + 4) * 8 * 10
     >>> res = chain(add.s(4, 4), mul.s(8), mul.s(10))
-    proj.tasks.add(4, 4) | proj.tasks.mul(8)
+    proj.tasks.add(4, 4) | proj.tasks.mul(8) | proj.tasks.mul(10)
 
 
 Calling the chain will call the tasks in the current process
 and return the result of the last task in the chain::
 
-    >>> res = chain(add.s(4, 4), mul.s(8), mul.s(10))
+    >>> res = chain(add.s(4, 4), mul.s(8), mul.s(10))()
     >>> res.get()
     640
 
@@ -492,7 +492,7 @@ And calling ``apply_async`` will create a dedicated
 task so that the act of calling the chain happens
 in a worker::
 
-    >>> res = chain(add.s(4, 4), mul.s(8), mul.s(10))
+    >>> res = chain(add.s(4, 4), mul.s(8), mul.s(10)).apply_async()
     >>> res.get()
     640
 
@@ -612,8 +612,8 @@ that it works on the group as a whole::
     [4, 8, 16, 32, 64]
 
 The :class:`~celery.result.GroupResult` takes a list of
-:class:`~celery.result.AsyncResult` instances and operates on them as if it was a
-single task.
+:class:`~celery.result.AsyncResult` instances and operates on them as
+if it was a single task.
 
 It supports the following operations:
 
@@ -738,11 +738,11 @@ Example implementation:
         raise unlock_chord.retry(countdown=interval, max_retries=max_retries)
 
 
-This is used by all result backends except Redis and Memcached, which increment a
-counter after each task in the header, then applying the callback when the
-counter exceeds the number of tasks in the set. *Note:* chords do not properly
-work with Redis before version 2.2; you will need to upgrade to at least 2.2 to
-use them.
+This is used by all result backends except Redis and Memcached, which
+increment a counter after each task in the header, then applying the callback
+when the counter exceeds the number of tasks in the set. *Note:* chords do not
+properly work with Redis before version 2.2; you will need to upgrade to at
+least 2.2 to use them.
 
 The Redis and Memcached approach is a much better solution, but not easily
 implemented in other backends (suggestions welcome!).
@@ -815,9 +815,9 @@ to call the starmap after 10 seconds::
 Chunks
 ------
 
--- Chunking lets you divide an iterable of work into pieces,
-   so that if you have one million objects, you can create
-   10 tasks with hundred thousand objects each.
+Chunking lets you divide an iterable of work into pieces, so that if
+you have one million objects, you can create 10 tasks with hundred
+thousand objects each.
 
 Some may worry that chunking your tasks results in a degradation
 of parallelism, but this is rarely true for a busy cluster

docs/whatsnew-3.0.rst

@@ -299,7 +299,7 @@ Tasks can now have callbacks and errbacks, and dependencies are recorded
 
                 $ dot -Tpng graph.dot -o graph.png
 
-- A new special subtask called ``chain`` is also included::
+- A new special subtask called ``chain`` is also included:
 
     .. code-block:: python
 
@@ -351,7 +351,7 @@ transport option, which must be a list of numbers in **sorted order**::
 
 Priorities implemented in this way is not as reliable as
 priorities on the server side, which is why
-nickname the feature "quasi-priorities";
+the feature is nicknamed "quasi-priorities";
 **Using routing is still the suggested way of ensuring
 quality of service**, as client implemented priorities
 fall short in a number of ways, e.g. if the worker
@@ -383,7 +383,9 @@ accidentally changed while switching to using blocking pop.
   since it was very difficult to migrate the TaskSet class to become
   a subtask.
 
-- A new shortcut has been added to tasks::
+- A new shortcut has been added to tasks:
+
+    ::
 
         >>> task.s(arg1, arg2, kw=1)
 
@@ -395,7 +397,9 @@ accidentally changed while switching to using blocking pop.
 
         >>> (add.s(2, 2), pow.s(2)).apply_async()
 
-- Subtasks can be "evaluated" using the ``~`` operator::
+- Subtasks can be "evaluated" using the ``~`` operator:
+
+    ::
 
         >>> ~add.s(2, 2)
         4
@@ -839,7 +843,7 @@ In Other News
 - Worker/Celerybeat no longer logs the startup banner.
 
     Previously it would be logged with severity warning,
-    no it's only written to stdout.
+    now it's only written to stdout.
 
 - The ``contrib/`` directory in the distribution has been renamed to
   ``extra/``.
@@ -878,7 +882,7 @@ Internals
     :mod:`celery.utils.functional`
 
 - Now using :mod:`kombu.utils.encoding` instead of
-  `:mod:`celery.utils.encoding`.
+  :mod:`celery.utils.encoding`.
 
 - Renamed module ``celery.routes`` -> :mod:`celery.app.routes`.