Adds documentation for System.import

This adds documentation for `System.import` and adds it to the Functions group. Happy to move it somewhere else if there is a better place. Fixes #239
Browser compatibility for es6

Adds a note about browser compatibility for es6 syntax with PhantomJS.
Fixes tests not running in Travis

Tests weren't running in Travis because we were using Testee #master
which had changed the way it's Grunt task worked. So I'm updated the
task and set a version number of Testee to use so this doesn't happen
again.
Merge pull request #263 from bitovi/es6-phantom

Browser compatibility for es6
Merge branch 'testee' into minor
Merge branch 'system-import-docs' into minor
Make steal.dev.log work in Node

steal.dev.log was expecting to have a `window` which caused it not to
work in Node. This is a problem because steal calls `steal.dev.log`
after it starts up, and will do that even in Node (such as when running
    builds). This fixes #246
New build

This fixes the build, I incorrectly ran a build against an older version of es6-module-loader in this commit: https://github.com/bitovi/steal/commit/a3d18b3c59dd94379f977c8e683247d0a7ba2c82

This should fix it.
Merge pull request #268 from bitovi/proper-build

New build
Merge pull request #2 from bitovi/minor

Sync with bitovi:minor