Travis Notes:

- Use http://lint.travis-ci.org/ to make sure it is valid yaml.
- Make sure all of your "-" lines start on the same column
- Make sure all of your "if" lines are aligned with the "else" and "fi" lines
- "If" blocks must be on one travis statement and have semicolons at the end of each line:

```
    - if [[ $TRAVIS_PYTHON_VERSION == 2.7 ]]; then
        echo "2.7";
      else
        echo "Not 2.7";
      end
```

- "If" blocks cannot contain comments
- All travis commands are run with `eval` and quotes are taken as literal characters
  unless you wrap the whole line in quotes:
`echo "hello : world"` is interpreted as `echo \"hello : world\"`
`"echo 'hello : world'"` is interpreted as `echo 'hello : world'`
`"echo 'hello : '$(MYVAR)'world'"` is interpreted as `echo 'hello : $(MYVAR)world'`
- Use `travis_retry` before a command to have it try several times before failing
  (useful for installing from third party sources)