* I dislike the global infection RSpec does. This commit is a first step
to get a rid of it.
* Also remove the need for `require 'spec_helper` in each spec file with
adjusting `.rspec`.
* I do not use 1.9.3
* Also keeping them in each file increases mental overhead (true it *can* be autoamted)
* None of the files encodes NON ASCII chars.
* I do not expect it makes any difference, since nobody programmatically
will consume strings generated by mutant under the assumption they are UTF-8 encoded.
* 1.9.3 Users have to deal with the encoding fuckup under ruby anyways.
* This specs still have spec per method granularity
* But one file specs multiple methods
* Compatible with mutant spec selector
* Deduplicates boilerplate unit setup
