Merge pull request #3 from servo/safe-mutex

Ensure that StringCache is locked before use through the type system.
Use cast instead of transmute from u64 to uint.

Fixes build error on 32-bit targets.
Merge pull request #4 from mbrubeck/32bit

Use cast instead of transmute from u64 to uint.
Upgrade Rust.
Merge pull request #5 from servo/rustup-20140716

Upgrade Rust.
Add Hash to derived trait implementations for Atom.
Merge pull request #6 from glennw/add-hash

Add Hash to derived trait implementations for Atom.
Generate documentation with rustdoc
Merge pull request #7 from servo/rustdoc

Generate documentation with rustdoc
Change to derive Hash, remove Str so Equiv is not implemented.
Merge pull request #8 from glennw/impl-hash

Remove Str implementation for Atom, so Hash can be derived.
Add the option of building with Cargo
Import macro-based static atoms from html5ever
Re-export atom::Atom at top level
Fixes for Servo's older Rust