Added MapBuffer convenience functions for slices
Fix code design for the program type

As discussed in #143, it's better to attach the `Unuse()` function to
the type, even if it doesn't use it, rather than a standalone function
like before (`programUnuse()`)
Add function to unbind a vao (fix #143)
Merge pull request #146 from tbruyelle/add-vao-unbind

Add function to unbind a vao (fix #143)
Merge pull request #147 from tbruyelle/fix-code-design

Fix code design for the program type
Update AUTHORS
Merge pull request #148 from tbruyelle/patch-2

Add tbruyelle to AUTHORS
Added a scary warning message
Merge pull request #144 from PolyFloyd/buffermap

Added MapBuffer convenience functions for slices