Add support for travis and coveralls.

This works by running tox inside travis, rather than duplicating the tox
config in travis syntax. The big win here is that coverage collects across
all the Python versions and then submits the combined result to coveralls.

.coveragerc

@@ -0,0 +1,20 @@
+[run]
+
+# Measure coverage of both tests and wrapt module.
+source =
+    tests
+    wrapt
+
+# This doesn't run the tests in parallel, it just causes the output to land
+# in uniquely-named .coverage.* files to be combined at the end of running
+# tox over the matrix.
+parallel = true
+
+[paths]
+
+# For the coverage combine command, consider these paths equivalent with
+# the first one being primary.
+src =
+    src/
+    .tox/*/lib/*/site-packages/
+    .tox/pypy*/site-packages/

.travis.yml

@@ -0,0 +1,13 @@
+language: python
+python: 2.7
+env:
+  global:
+    - COVERAGE_CMD="coverage run -m"
+    - COVERAGE_DEP=coverage
+install:
+  - pip install tox coveralls
+script:
+  - tox
+after_script:
+  - coverage combine
+  - coveralls

tox.ini

@@ -14,10 +14,10 @@ envlist =
 
 [testenv]
 deps =
+  {env:COVERAGE_DEP:}
   pytest
-  pytest-cov
 commands =
-  py.test -v --cov wrapt --cov-report html []
+  {env:COVERAGE_CMD:} py.test -v []
 
 [pytest]
 norecursedirs = .tox venv