Move toward tox testing for TravisCI.

This is used by Bioblend, Pulsar, and Planemo and provides several benefits:

 - More flexibility then baking logic directly into .travis.yml
 - Makes the CI testing more portable
 - Generally leads to more parallelism on Travis
 - "prettier" display of results (things are broken down by the kind of test).

For the last two points - compare https://travis-ci.org/galaxyproject/galaxy and https://travis-ci.org/galaxyproject/planemo.

I would like to add the qunit tests to Travis and I see this a good first step toward being able to do that well.

.travis.yml

@@ -1,9 +1,13 @@
 language: python
-python:
-  - "2.7"
-  - "2.6"
+python: 2.7
+env:
+  - TOX_ENV=py27-lint
+  - TOX_ENV=py26-lint
+  - TOX_ENV=py27-unit
+  - TOX_ENV=py26-unit
+
 install:
-  - virtualenv .venv
-  - . .venv/bin/activate
-  - pip install flake8
-script: ./.ci/flake8_wrapper.sh && ./run_tests.sh -u
+  - pip install tox
+
+script: tox -e $TOX_ENV
+

tox.ini

@@ -0,0 +1,22 @@
+[tox]
+envlist = py27-lint, py26-lint, py27-unit, py26-unit
+skipsdist = True
+
+[testenv:py27-lint]
+commands = bash .ci/flake8_wrapper.sh
+whitelist_externals = bash
+deps = flake8
+
+[testenv:py26-lint]
+commands = bash .ci/flake8_wrapper.sh
+whitelist_externals = bash
+deps = flake8
+
+[testenv:py27-unit]
+commands = bash run_tests.sh -u
+whitelist_externals = bash
+
+[testenv:py26-unit]
+commands = bash run_tests.sh -u
+whitelist_externals = bash
+