chore(travis): implement continuous integration strategy using Travis-CI

It may unfortunately be necessary to cut back and rely on browsers available on Travis, but I'm hoping
this is not the case.

Closes #13
chore(travis): build logs dir (used by SL scripts)

I omitted these initially, but it would take effort to find a way to make this work without the
logging.
chore(dependencies): install karma-sauce-launcher on TravisCI

Self-explanatory change, the sauce launcher is required to launch these browsers on the CI server.
chore(karma): add IE* custom browsers for CI

These will be removed if they are too expensive (or if anyone tells me to!), but ideally this library
should support IE9.
chore(travis): use LOG_INFO rather than LOG_DEBUG for karma logLevel

There is a bit too much spammy output on Travis, this can be disabled for now.
chore(travis): don't run tests on so many browsers, just to see what happens

SL seems to not be running any tests even though it's connecting just fine.

This makes me very sad, and I don't want to have to talk to their support staff to figure out the
problem. Sigh :(
chore(travis): print logs after running

Another self-explanatory change.