Test with pypy and enable coveralls in AppVeyor

* Install pypy using chocolatey
* Enable coveralls test environment in AppVeyor
* Suggest maintaining build matrix in .travis.yml by using "tox --listenvs"

 Fix #1254

.travis.yml

@@ -7,25 +7,25 @@ install: "pip install -U tox"
 # # command to run tests
 env:
   matrix:
+    # coveralls is not listed in tox's envlist, but should run in travis
     - TESTENV=coveralls
-    - TESTENV=doctesting
+    # note: please use "tox --listenvs" to populate the build matrix below
     - TESTENV=flakes
     - TESTENV=py26
     - TESTENV=py27
-    - TESTENV=py27-cxfreeze
-    - TESTENV=py27-nobyte
-    - TESTENV=py27-pexpect
-    - TESTENV=py27-subprocess
-    - TESTENV=py27-trial
-    - TESTENV=py27-xdist
-    - TESTENV=py33
     - TESTENV=py33
     - TESTENV=py34
-    - TESTENV=py35-pexpect
-    - TESTENV=py35-trial
-    - TESTENV=py35-xdist
     - TESTENV=py35
     - TESTENV=pypy
+    - TESTENV=py27-pexpect
+    - TESTENV=py27-xdist
+    - TESTENV=py27-trial
+    - TESTENV=py35-pexpect
+    - TESTENV=py35-xdist
+    - TESTENV=py35-trial
+    - TESTENV=py27-nobyte
+    - TESTENV=doctesting
+    - TESTENV=py27-cxfreeze
 
 script: tox --recreate -e $TESTENV