TST: update .travis.yml

[rgommers]

I turned on TravisCI for this repo. Would be good to have it working before merging other PRs.

Changes in this PR are basically a subset of relevant changes to scipy/.travis.yml.

[pv]

Maybe replace scipy.lib.six by six and add that as dependency? Maybe specify sudo: false and use the addons section instead of apt-get for installing the packages.

[rgommers]

Fine with me to add six as a dependency. Could be vendored in this repo, but it's a very light dependency.

[rgommers]

Or even better, just replace the import with:

PY3 = sys.version_info[0] == 3
if PY3:
    string_types = str
    import builtins.open as _open
else:
    string_types = basestring,
    import __builtin__.open as _open

Then no dependency on six or scipy._lib.six is needed.

[rgommers]

Maybe specify sudo: false and use the addons section instead of apt-get for installing the packages.

Adding sudo: false. I don't get the addons section - I am doing that in this PR already right?

[pv]

Otherwise LGTM

[rgommers]

tests passed

[rgommers]

Okay, merging then. Thanks @pv