Check for rspec being loaded in custom matchers

* Possible travis fix?
Basically working, doesn't contain absolute paths for file and directory.
Remove whitespace in front of compiler commands.
Added feature tests for the JSON compilation database reporter.
Updated README with json-compilation-database.
Split up JSON db tests, moved magic number to constant.
Added spec for format_compile_command()
Use workaround for http://luan-itworld.blogspot.de/2013/08/ruby-undefined-method-for.html
Use json_pure on older rubies if available.
Added missing require json.
Install json_pure to make tests work for ruby 1.8.7
vendor JSON generator/parser for ruby 1.8

* Use json in stdlib for ruby 1.9+
* Change dashes in file names to underscores to match convention
Clean up files after feature runs
Simplify steps
Fix relative path loading