Promises & some cleanup

[dougmoscrop]

I hope I wasn't overzealous in these changes; some of it was to get it working on Windows (test/coverage/etc).

Here's a list of things I did in the cleanup commit:

• Switched from jshint to eslint (I found jshint was behaving weird and missing things?) -- Required less configuration too -- Also made it differentiate between things that are okay in test vs. in lib
• Factored mocha options just in to a file instead of repeated in scripts
• I moved linting to after test, this is mostly personal preference but I like to be able to troubleshoot test failures without the linter yelling at me until after the tests pass
• Travis should do the coveralls part now (this is the only thing I didn't actually test), so the developer side doesn't get any kind of error
• Istanbul instead of jscoverage. I think the scripts are a lot simpler/cleaner now including getting rid of some globals/funkyness in the common.js file

The second commit is to address https://github.com/ncb000gt/node-es/issues/58 in a backwards compatible way.

Thoughts?

Edit: I noticed I did not run the functional tests in the new test script. I'll push a fix now.

[dougmoscrop]

Looks like the coveralls part works, but there was a bit of a decline. I don't know if that's just difference in instrumentation or not - I can poke around and try to get coverage back up.

[brozeph]

In general, I like the direction of this - I was not familiar with thenify, but after looking closely at that library, I like how the module supports backwards compatibility with callback usage as well and it appears to be seamless.

[dougmoscrop]

So the code coverage reduction seems more a byproduct of the change to istanbul than anything else. Based on the coverage report I don't see a way to add much more coverage without getting in to more elaborate / brittle testing scenarios.

[brozeph]

Merging this PR to prepare an NPM release... another PR inbound shortly.