Merge pull request #31 from RReverser/master

Added estraverse.VisitorOption.Remove / this.remove()
Support ES6 node traversing
version 1.6.1-dev starts
Suppress lint errors
Add Visitor.keys API
Updated development deps.

Fixed Mocha command after update (see jashkenas/coffeescript#3349).
Added tests for skip & break.
Small test cleanup (using object destructuring assignment).
Fixed controller test (didn't use local instance with collected logs at all).
Added tests for `estraverse.replace`.
Fixed node removal according to found bugs.