_.getPath and _.hasPath enhancements

I needed _.getPath to support accessing arrays and I did not find it in the docs so I came here to add the feature, but when running the tests, I did find it. So I...

- documented array accessing through parameters in the docs
- added possibility of having composite paths in array parameters (examples in the docs)
- fixed jshint tests not passing because of indentation in Gruntfile.js

Unresolved concerns my code may generate:

- How will the extra checks in _.getPath and _.hasPath impact performance? Is that something to watch closely?
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