Release Name: 0.2.0

Notes:
Finally the overdelayed release of 0.2.0.




Changes:
* Added paths option to has_library?
* Added Generator#abort! for when that critical library just isn't there.
* Added Zed Shaw's rakehelper lib (from rfuzz, with permission).
* Extensions using mkrf can now build properly in RubyGems!
* Extension configurations should now be named mkrf_conf.rb to not conflict with the mkmf settings in RubyGems.
* Added example extensions.
* Add install task to generated Rakefile.
* Preprocessor define handling moved to Availability from Generator.
* find_executable method added to Availability.
* include_header and has_header? now properly set preprocessor defines.
* Defaults on Generator work again. [44]