Cargoify

Doesn't replace the Makefiles, but lets other projects
use gfx-rs in an easy way.

Closes #110
Re-enable gitter-travis integration
Merge pull request #130 from cmr/cargo

Cargoify
Make triangle example compile
Make cargo generate dylib for gfx_macros
Merge pull request #131 from amaranth/fix_example

Make triangle example compile
Merge pull request #132 from amaranth/cargo

Make cargo generate dylib for gfx_macros
Rewired texture and sampler binding, provided access from the user side. Implemented bundle pre-binding and texture binding.
Improved texture creation and binding, stored TextureInfo in the device, implemented error codes for bind_shader_bundle.
Cube - generated cube mesh, fixed indexing support.
Cube - perspective projection added
Implemented sampler binding, fixed a bunch of critical errors in our texturing and shader parameters code.
Fixed mipmap range and LOD limits, updated Cube shaders
Added Cargo config to the triangle example. Removed examples compilation from the Makefile.
Fixed program parameter debug conditions. Fixed Cube README.
Implemented better erroring on TextureHandle encountered as a shader parameter.
Removed unused GlProvider::is_extension_supported()
Merge pull request #136 from Kimundi/master

Removed unused GlProvider::is_extension_supported()
Merge pull request #133 from kvark/texture

Texturing and Cube example
Renamed 'rast' to 'state'