Replace removed deprecated method call

`move_iter` was deprecated, now it’s gone altogether.
Merge pull request #34 from chris-morgan/patch-1

Replace removed deprecated method call
atom: Slight efficiency optimization in string interning
Merge pull request #35 from pcwalton/list-optimization

atom: Slight efficiency optimization in string interning
Fix PartialOrd for Atom

This snuck in during a Rust upgrade.
Add tests for low-level representation
Add more comprehensive benchmarks
Consolidate packing / unpacking code

Mostly for safety and maintainability.  Between repr.rs and the representation
tests in atom/mod.rs, we now have

Thanks to the magic of LLVM's inlining and SROA, this code is faster on some
benchmarks and not significantly slower on any.

Also added debug_assert!s and changed the existing non-test assert!s.  I
believe they're all safe to omit in release builds.
Use #[unsafe_no_drop_flag] so that Atom can be only 64 bits

Drop flags are going away, hopefully, but in the mean time here's a simple fix.
Use lazy-static for the global hash table
Use XXHash instead of SipHash

This is an approximately 8% speedup on interning a 56-byte string.
Add optional event logging

We can use this with Servo to generate traces from real websites for
optimization purposes.
Add an example for event logging