Use nsdeclare for namespace declarations

This PR uses the `nsdeclare` module for namespace declarations.

Changes:

* Better output - `nsdeclare` avoids redeclaration of already declared namespace parts
* DRY - use the same module as other Grunt plugins
* Namespace declarations don't all happen at the top of the file, they happen inline
* Consistently append `Regex` to cached regular expression variable names
* Consistently use lowecase `filepath` to match `filename`
* Put default values of options on a new line as intended in README