Removing 'comparator` overloads of `distinct`

Removing these fairly recently added overloads as they turn out to not be the best approach.

Discussion ongoing as to how to implement them at https://github.com/Netflix/RxJava/issues/395
Merge pull request #400 from benjchristensen/distinct-comparator

Removing 'comparator` overloads of `distinct`
Update CHANGES.md
0.14.0-SNAPSHOT