Fix typos.
Merge pull request #11 from waywardmonkeys/typo-fixes

Fix typos.
Create AUTHORS
Update glfw headers and OSX lib
Added StringBuilder::SubstituteAll methods plus test
Added StringBuilder::Contains method and test
Filename upper/lower case fix
Some Linux work (still crashes because required but unsupported GL extensions aren't checked yet
glExt::Discard and IsValid methods
Allow assigning null string pointers to String and StringBuilder
Fixed GL initialization on OSX, apparently it's an error to query the GL_EXTENSIONS string if the Core Profile is used
Fixed broken ShaderTest