needs better name?

Conflicts:
	lib/ruby_parser/bm_sexp.rb

* Cleans up duplicated logic for skipping files
* This is not being used for the install_rake_task behavior

closes #164

User could compare with the **baseline** json file ignore base directory.

instead of returning false for options[:exit_on_warn]

instead of when reporting, which lead to confusion
and filtering all over the place instead of in one place.

although we're still depending on "globals",
just not ones shared with every Ruby app

for modularity and easier reuse by external libs

--no-progress turns it off