Separated Server and Worker pools.

There are now some generic classes, MicroServer and MicroWorker
which respectively handle the servers (TCP, SSL or UNIX) and the
pool of workers, ready to process the requests.

They will serve as the basis for both Prax and Racker.
Rake test task.
Overall rewrite/refactor of Prax::Handler and Prax::Spawner.

Highly unstable and likely very broken.
Fixed overall bugs.
More corrections to Prax handler, spawn & request.

- Application now correctly spawns the application;
- Request correctly proxies the request to the application;
- Response expects a request to be processed in 60 seconds;
- Config was cleaned up of useless methods.
Complete rewrite/refactor of Racker.
Fixed content_type for unknown public file.
Application killer, corrections and better logs.
Fixed a stalled socket bug.
Feature: port forwarding.
Added prax uninstall command

As raised by #46 there was no way to easily uninstall Prax. Until
now :)
Fix: executable flag on uninstall command.
Racker exports ENV vars from .env file

It will export any environment variable defined in the `.env` file
before starting your application, hence making them available
without requiring the `dotenv` gem (for example).

It will also source any `.praxrc` file so you may configure things
to your needs (eg: chruby or something). This must be a bash script.
Fix: restart and autokill respawned apps after TTL

Two bugs were fixed: the first one prevented apps to be restarted
using `prax restart` (or `touch tmp/restart.txt`); the second one
prevented Prax::Monitor to autokill an app once it had kill it once.
Updated README with features.
Typo in README
Racker sets REMOTE_ADDR as 127.0.0.1 when talking on UNIXSocket.

Prax already sets the X-FORWARDED headers. It is up to the Rack
applications to determine what they must believe.
Synced with master
Disabled unit tests (they don't run for some reason).
Implements FQDN resolution.