adding python daltonize from moinmoin (modified)
calling the python script from the gem

* updated error handling
* trying to capture and raise errors back to the user
updated readme for the python version
updated readme
updated readme
new version of the algorithm
adapting python version to use ruby - launching external process
merging @jcupitt's version in daltonize.rb

* daltonize.rb can be run standalone
* it is also launched from carrierwave
moved daltonize.rb to lib

* daltonize.rb code being called from carrierwave-daltonize
* no dependency on carrierwave-vips, only vips
* can be used together with MiniMagick, Rmagick etc
updated README
add alpha handling and cli version

Add alpha handling.

Add a command-line version, and an implementation in nip2 for testing,
see the README. There's a test image too.

Small clarifications to the comments.
Merge branch 'ruby' + pull #2

* moving other/daltonize.rb into lib
* updating the code and fixing small bugs
* re-using lib/daltonize.rb inside the carrierwave plugin
* updated documenation etc