Add python3.5, pypy3, and latest git to travis

.travis.yml

@@ -4,7 +4,10 @@ env: # These should match the tox env list
     - TOXENV=py27
     - TOXENV=py33
     - TOXENV=py34
+    - TOXENV=py35
     - TOXENV=pypy
+    - TOXENV=pypy3
+    - TOXENV=py27 LATEST_GIT=1
 install: pip install coveralls tox
 script: tox
 # Special snowflake.  Our tests depend on making real commits.
@@ -13,6 +16,13 @@ before_install:
     - git config --global user.email "user@example.com"
     # Our tests inspect some of *our* git history
     - git fetch --unshallow
+    - git --version
+    - |
+        if [ "$LATEST_GIT" = "1" ]; then
+            ./latest-git.sh
+            export PATH="/tmp/git:$PATH"
+        fi
+    - git --version
 after_success:
     - coveralls
 sudo: false
@@ -20,3 +30,9 @@ cache:
     directories:
         - $HOME/.cache/pip
         - $HOME/.pre-commit
+addons:
+    apt:
+        sources:
+            - deadsnakes
+        packages:
+            - python3.5-dev