Test runner invocation, ES2016, Coveralls repetition

[novemberborn]

Some thoughts on the tutorials:

• Both the mocha and AVA tutorials come with a --timeout option in the example. This isn't necessary for nyc support
• It seems to me the Coveralls sections could be in their own document, with links
• Especially for AVA it's likely that users want to set up ES2015 support, so we should link to that tutorial

I should have some time to make these changes if folks think they're a good idea.

(Nice site by the way!)

[bcoe]

@novemberborn would love the help.