Use Rack Test

[johnboyes]

Creating this as an enhancement after a discussion with @lashd. Using Rack Test will be a performance enhancement in terms of speed.

[lashd]

Thanks @johnboyes. To give a little more detail.

What I am thinking is that where people are unit testing code that makes http calls it could be useful to have mirage served by something like the rack/test framework. I.e. Have requests served without the need to start mirage as a separate process and get http clients to go 'over the wire'. This would certainly make test suites run more quickly.