* `Call` is the mechanism for request execution. It encapsulates a single request action either synchronously or asynchronously, and can support canceling.
* `CallAdapter` is a means of supporting a method return type other than `Call` (like RxJava's `Observable`) by adapting the `Call` instance into another instance. This change moves RxJava support into a sibling module which uses an adapter for supporting `Observable` types.
* `Response` represents the HTTP response along side the deserialized body. It allows access to both the converted body and lower-level items such as the header, response code, and underlying OkHttp request and response objects.

Consolidate samples into a single package.

Normalize specifying encoded values via parameter annotations.

Switch to OkHttp's built-in form body builder.

Remove our RequestInterceptor.

Use OkHttp's Interceptors for adding headers, query parameters, or modifying the path.

Includes this repo in our open source bug bounty program.

Fix foo/bar/baz in @Query documentation

Add ProGuard config to the website

Remove 'set' prefix from builder methods.

HTTP 204 & 205 should skip the converter.

Restore Form URL encoding support.

resolves #117

Changes to Javadoc to remove doclint errors and warnings

JDK 8 introduced doclint to the javadoc tool:
http://openjdk.java.net/jeps/172

Unfortunately, this causes deployments to fail under JDK 8, due
to javadoc doclint errors.

Not all warning messages were removed, but `mvn javadoc:jar` now
completes without an early failure.

Further discussion will be required to decide on how to approach the
doclint warnings.

Remove Client, Request, Response, TypedInput, and TypedOutput abstractions.

Remove specialized ConversionException.

Simplify custom HTTP method implementation.

Prefer normal IOExceptions or any RuntimeException for unexpected things.

Get rid of our own Header class.

Use OkHttp as the sole client.

Pass request body type to converter for serialization.