Merge pull request #104 from bvssvni/master

Reexported `OpenGL` from shader_version
Merge pull request #105 from bvssvni/master

Fixed deprecated warnings for piston-image
Merge pull request #106 from bvssvni/master

Added metadata to Cargo.toml, renamed package
Implement `GlyphCache::opt_character()`
Merge pull request #108 from cybergeek94/master

Implement `GlyphCache::opt_character()`

Build passed, this looks good to merge.
Upgraded to latest Rust