Added a glsl parser
Merge branch 'master' of github.com:vispy/experimental

* 'master' of github.com:vispy/experimental:
  arg, forgot to save before commit
  ak_shader_combing: add example related to transforms
  ak_shader_combing: some refactoring and docs++
  ak_shader_combining: Works now, but not quite happy yet
  Updated proof of concept for mplexporter.
  Experimenting with a Vispy backend for matplotlib, using mplexporter.
  Added plotting interface demo.
  Updated scatter examples.
  Updated scatter demo after Luke's changes.