Relax failed_results_re.

rspec-core’s formatting has changed a bit. The
backtrace used to be formatted like so:

[36m     # ./spec/autotest/failed_results_re_spec.rb:31:in `block (4 levels) in <top (required)>'[0m
[36m     # ./spec/autotest/failed_results_re_spec.rb:6:in `block in run_example'[0m
[36m     # ./spec/autotest/failed_results_re_spec.rb:18:in `run_group'[0m
[36m     # ./spec/autotest/failed_results_re_spec.rb:8:in `run_example'[0m
[36m     # ./spec/autotest/failed_results_re_spec.rb:31:in `block (3 levels) in <top (required)>'[0m
[36m     # /Users/myron/code/rspec-dev/repos/rspec-core/exe/rspec:4:in `<top (required)>'[0m

…but is now formatted like so:

     [36m# ./spec/autotest/failed_results_re_spec.rb:31:in `block (4 levels) in <top (required)>'[0m
     [36m# ./spec/autotest/failed_results_re_spec.rb:6:in `block in run_example'[0m
     [36m# ./spec/autotest/failed_results_re_spec.rb:18:in `run_group'[0m
     [36m# ./spec/autotest/failed_results_re_spec.rb:8:in `run_example'[0m
     [36m# ./spec/autotest/failed_results_re_spec.rb:31:in `block (3 levels) in <top (required)>'[0m
     [36m# /Users/myron/code/rspec-dev/repos/rspec-core/exe/rspec:4:in `<top (required)>'[0m

This change makes the regex tolerant of the ANSI color code
being anywhere between the start of the line and the `#`.
Rspec2 -> RSpec

There’s no good reason to include the rspec version number.
Make this gem always work, not just when `.rspec` is defined.

This addresses https://github.com/rspec/rspec-core/pull/1051
Autotest::RSpec -> Autotest::Rspec.

Autotest’s auto discovery mechanism only works properly
when we name the constant `Rspec` since that’s how it
maps `rspec`.