Solved the Great Response Crisis of Week 8

By coercing lifetimes instead of types and moving from_http to its own trait, we have
managed to both allow new Response representations and remove all the lifetimes from
everywhere.

Such is the power of Sundays.
Why are you transmuting this to what it already is? This is a bit risky and it could be avoided by defining the trait as

```Rust
pub trait HttpResponse<'a, 'b> {
    fn from_http(&'a mut ResponseWriter<'b>) -> Self;
}
```