Ignore .config, which is dynamic output from setup.rb
Fixes SciRuby/rb-gsl#7: undefined constants
Fixes SciRuby/rb-gsl#8: missing porting.h
Won't permit prerelease versions unless all constraints contain prerelease version numbers
Update gemfile to match gemspec
More ignores
Merge branch 'master' of https://github.com/Zenexer/rb-gsl into Zenexer-master

Conflicts:
	Gemfile
	gsl.gemspec
Cleanup extra copy of porting.h