The monkey patch adds instance method Hash#fn, which returns a copy of the hash
as a FunctionalHash.

Example:

    regular_hash = {a: -> { "hello" } }
    regular_hash[:a]
    # => #<Proc ... >
    FunctionalHash.enable!
    regular_hash.fn[:a]
	# => "hello"

Also...

  * loads Gemfile.dev from Gemfile, and .gitignores Gemfile.dev.

Version bump to v0.2.0