Implement ruby_blocks matching support.

Added matcher implementation and spec. Cucumber tests are missing.
Implement ruby_blocks matching support.

Add unstaged changes from previouse commit.
Add documentation for 'ruby_block' matcher.
Rename create_ruby_block matcher.

'create_ruby_block' matcher has been renamed to 'execute_ruby_block' project's maintainer recommendations.
Merge pull request #84 from andrey-vorobiev/master

Add support for ruby_block resource