Add MIME-typoe parser draft
Add default encode/decode implementations
Allow override detected MIME type
Add API docs
Allow parse with alias

``` ruby
HTTP.get("...").parse :json
```
Support MIME type aliases within chainable API
Bring back json encoding
Bump up YARDstick threshold
Fix specs for Ruby 1.8.7
Restore info about JSON syntax sugar
Merge pull request #93 from tarcieri/feature/mime-type-parse

Brings back MIME-type parser/emiter