Added PyPy 3 to the build matrix.

Also, I removed the custom PPA since they are available by default.

.travis.yml

@@ -8,15 +8,9 @@ env:
     - TOXENV=3.3
     - TOXENV=3.4
     - TOXENV=pypy
+    - TOXENV=pypy3
 before_install:
   - |
-    if [[ $TOXENV = pypy ]]; then
-      deactivate
-      sudo apt-add-repository --yes ppa:pypy/ppa
-      sudo apt-get update
-      sudo apt-get install pypy
-      source ~/virtualenv/pypy/bin/activate
-    fi
     python --version
     uname -a
     lsb_release -a