Added a basic Rast module to the generic device and GL backend.
Improved the primitive state, fully implemented on GL backend
Depth test implemented in the GL back-end
Moved DrawState into the render module and exposed to the user.
Added cull & depth helpers for DrawState
Added Blend state types.
Blend mode setup implemented on the GL back-end
Implemented basic blend presets.
Merge pull request #83 from cmr/master

Update to master
Fixed face culling, enabling by default now.
Merge pull request #79 from kvark/rast

Basic rasterizer states
Load extension strings using gl::GetStringi rather than gl::GetString

gl::GetString(gl::EXTENSIONS) is not supported in forward compatible contexts, and returns a null pointer (segfault ahoy!)
Merge pull request #85 from cmr/master

Travis-Gitter
Move glfw platform implementation into separate crate

Separate platform implementations should be in different crates. In the future we will also have `sld2_platform` for example.
Merge pull request #86 from bjz/glfw_platform

Seems fine so far.
Add version information querying and logging
Implement fallback for querying extensions when the gl version is < 3.2
Merge pull request #84 from bjz/capabilities

Load extension strings using gl::GetStringi rather than gl::GetString
Added Glfw window context creation with fallbacks.
Made the default one try OpenGl 3.2 core and 2.1, in that order.
moved info log message