.travis.yml: run tests on both Linux and OSX; use tox to setup virtual env and install deps, and pytest to discover/run tests

.travis.yml

@@ -1,17 +1,41 @@
 sudo: false
+
 language: python
-python:
-  - "2.7"
-  - "3.3"
-  - "3.4"
-  - "3.5"
-  - "pypy"
-#  - "pypy3" # Disable pypy3 until Travis updates it to >= 3.3
+
+matrix:
+  include:
+    - python: 2.7
+      env: TOXENV=py27
+    - python: 3.3
+      env: TOXENV=py33
+    - python: 3.4
+      env: TOXENV=py34
+    - python: 3.5
+      env: TOXENV=py35
+    - python: pypy
+      env: TOXENV=pypy
+    - language: generic
+      os: osx
+      env: TOXENV=py27
+    - language: generic
+      os: osx
+      env: TOXENV=py33
+    - language: generic
+      os: osx
+      env: TOXENV=py34
+    - language: generic
+      os: osx
+      env: TOXENV=py35
+    - language: generic
+      os: osx
+      env: TOXENV=pypy
+
 install:
-  - pip install -vr requirements.txt
-  - make install
+  - ./.travis/install.sh
+
 script:
-  - make check
+  - tox
+
 notifications:
   irc: "irc.freenode.org##fonts"
   email: fonttools@googlegroups.com