Fixes scala version errors in json4s usage

Summary:
Some other things:
- Change package names to match folder heirarchy
- Fix a bug with finding the main.json file

Test Plan: Run SprayGenerator and see generated files with a sample spec

Reviewers: nitro, fb, prateek.pandey

Subscribers: eng

Differential Revision: http://phabricator.scale-data.com/D931
Use Scala 2.10, matching swagger-core.
Fix parsing/usage of dataType/paramType.

Looks like swagger-core has had a bug all along in how it parses
dataType/paramType, and we've just been working around it. Fix
swagger-core while avoiding having to wait for upstream by
forking just the piece that needs fixing: read paramType from
JSON as the "paramType" field instead of the "type" field.

Fix up our usages where we intended to use dataType but were
using paramType instead as a workaround.

Now, the real paramType will be available for us to use in
generating routes/marshallers that correctly handle the different
parameter types (such as "path", "query", and "body").
Improve URI and body param handling.

For URIs with multiple path segments, we need to use
spray-routing's DSL syntax for separating path segments because
just using a literal '/' character matches an escaped '/'
character in the URI string. In the process, start breaking the
premature abstraction which overly simplified spray-routing's
interface to assume paths could be represented as simple strings.

Receive the body parameter the way Swagger expects it to be
received: as the entire body, rather than as a named field within
the body. Since the type of this body is already defined, usually
as a Swagger model which we generate as a case class, just create
a type alias for the message classes we expect to plug into
marshallers. Given this is the only type of parameter we expect to
go into the body, it seems we should do away with the message
concept as well since its only purpose appears to be creating
marshallable structures out of the other parameter types (such as
"path" and "query") which we should receive from elsewhere in the
request rather than the body.