Fix/use rust url

- Use `rust-url`
 - Includes `rust-encoding` for component encoding of cookies
- Update for breaking `iron` changes
 - Examples
 - README
- Improve tests
 - Use `rust-test`

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`rust-crypto::util::fixed_time_eq` causes a segfault, and was replaced with `==`. An issue will be opened separately to track this.

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Fixes #29 
Unnecessary `unsafe` here. `iron-test` provides utilities for creating blank `Response` too, so you no longer have to do this kind of thing and risk random segfaults in tests.