Initial commit of migrating the documentation site to nandoc.

There are some layout problems, and we need to clean up the build pattern (including re-implementing guard and moving our assets into their own directory), but I wanted to get started on building the templates we'll be using.
Added Gemfile for dependency management
Guard now works with Nanoc and Livereload
added syntax highlighting as a filter for page compilation
Wrote the basics for our API resource helpers

Wrote the initial modules needed to keep our API resources as Ruby hashes and render them in any page using a special helper method.
Shuffled around constant definitions and added ACCOUNT_EDITABLE_FIELDS

In an attempt to shuffle compilation warnings in Guard, I shifted around the constant definitions, which didn't really have an effect. I'll probably move the constants into their own module file at a later date.

I also created the ACCOUNT_EDITABLE_FIELDS constant, which we can use to define what fields are editable for the account resource. This pattern will really help simply writing our documentation
Added helpers for HTTP statuses and headers

Since we want to include the expected HTTP Headers for each response, I added basic helpers for rendering HTTP status and headers (code yanked from: https://github.com/github/developer.github.com/blob/master/lib/resources.rb#L10)
Wrote first draft of Account method specifications and used helpers

The account object acted as a testbed for our new documentation generation practices, due to its simplicity.
Separated helpers and API Resources into separate files.

To help keep things managable, I have separated the helper methods from the API resource hashes.
Changed the Link URLs to be for Freckle.
Modified URL and timestamps of the account object.
Created our Entry Objects & the various simple objects it depended on

The objects created were:
* Entry
* The Editable fields for our entry object
* Simple Project Object
* Simple Tag Object
* Simple Invoice Object
* Simple Import Object
Wrote the first complete draft of the Entry Object Specification.
Made our paginations links reflect the resource being paginated.

I added an optional "pagination_resource" hash object, which can be used to rename the pagination links to be correctly named.
Fixed typo, added `imports` & `invoices` as parameters, pagination fix

`imports` and `invoices` are now two parameters we can filter by in our GET request, and the pagination is now named.
Wrote the first draft of the expense API
Added invoiced_at GET parameters, PUT action to mark entry as invoiced

Now users will be able to search for entries that have been invoiced within a specified date range, and can mark entries as invoiced outside of Freckle.
Use the proper URLs for Expenses
fixed indentation
added the 400 Bad Request status code