Shader#bind is now Shader.bind
Texture#bind is now Texture.bind
Refactor Texture.bind
Use latest build for samples, run without opengl

`require` latest build rather than latest installed version. This makes
it easier to test out samples for a new build without affecting the
currently installed rbSFML.

If opengl gem isn't installed, catch the LoadError and print an error,
so `rake samples` will still run.
Slight comment/whitespace tweak

The ruby-opengl gem is now just opengl. See
https://github.com/larskanis/ruby-opengl
Ignore doc/
Add gemspec
Ignore built gem file
Use sfml.rb instead of all.so
Add sfml.rb for requiring all SFML components
Add rake task for building gem
Don't copy sfml/all.so for gem
Fix copy, build gem, remove lib afterwards
Use all.so instead of sfml.rb
Move *.so location to simplify gem
Lowercase for gem name (suggested by rubygems.org)
Add description
Merge pull request #42 from silverhammermba/sfml_latest

Update for latest SFML
Merge pull request #44 from silverhammermba/fix_samples

Small Fixes for Samples
Merge pull request #45 from silverhammermba/gem

Make Into a Ruby Gem