Optimize `_.contains` by using native `String#contains` when available.
Merge pull request #432 from d10/master

Fix _.template docs typo. [ci skip]
Update docdown to fix doc bugs related to params that are properties of other params. [ci skip]
Minor tweaking, moving var order.
Add bad shim tests for String#contains and remove those for Function#bind as we don't use native bind.
Update the tested version of node in readme. [ci skip]
Use node --harmony for code coverage tests.
Use `Boolean` to fake out the `isNative` check and allow environments to test the native `String#contains` fork of `_.contains`
Simplify nvm use in travis.yml.