[UPDATE] Add Gemfile for compatability with Bundler
[REFACTOR] Use Knod as a namespace

This commit converts the `Knod` class into a module a-la typical Gem
organization and pulls out the `Request` class into a separate file. In
addition, the various server related methods are now part of the
`Server` class. The `Knod.start` interface has been preserved.
Merge pull request #2 from enocom/master

Use Knod as a module a-là typical Gem organization