gitconfig style configuration

[dchelimsky]

Add support for something like .rspecconfig or .rspecrc in the home and project directories, override-able on the command line.

[dchelimsky]

We should also deprecate spec.opts once this exists. See #12

[probablykabari]

http://github.com/RipTheJacker/rspec-core/commit/368a024d31b3ee2784fed8458cc152e92eef9639 , including #12 there

[dchelimsky]

http://github.com/rspec/rspec-core/commit/fd0398e9e8e61c69cf95aa9e41b440d0d622a095