Update Piston exmamples for latest version.
Upgrade to latest Rust nightly

See https://github.com/rust-lang/rust/pull/17853 for details.
Fix deprecation warnings
Disable style warnings in FFI code
Fix typo in constant name
Fix style warnings
Fix inconsistent names

Most constants were ommitting the LOAD_ prefix, some weren't.
Merge pull request #57 from hannobraun/cleanup

Cleanup
Merge pull request #54 from ssirai/fix

Update Piston exmamples for latest version.
Update to latest freetype-rs changes
Remove unnecessary dependencies
Suppress compiler warning