Merge pull request #62 from ozkriff/master

Updated to latest Rust: ~str -> StrBuf
Updated sax-rs
Updated glfw-rs
Insert .as_slice() where necessary to make gl-rs typecheck
Merge pull request #63 from gmorenz/master

Update to latest rust
Update submodules
StrBuf->String
Merge pull request #64 from bjz/string

StrBuf->String
Updated deps/sax-rs
Updated to latest Rust