Js and Grep test work with Guard.

We have a pattern in the Guardfile to watch when files under `lib/` are saved and then run the corresponding test. The `js.rb` and `grep.rb` files were located in directory structures that did not match their corresponding test files.

This moves the test files, so Guard will properly pick up changes when the source files are changed.

To test run:

    bundle exex guard

Then save either `lib/pre-commit/checks/grep.rb` or `lib/pre-commit/checks/js.rb`