Rename LaunchConfigFactory to LaunchConfigs (closes #294).
Remove some unneeded stuff.
Generalise the promise infrastructure so it can be used for more than just backgrounding.
Add a public mechanism for creating promises.
Generalise the Rx support to work with Ratpack promises.
Initial work on HTTP client (#217).

Far from done. Lots of missing functionality, no configurability and internals are a mess.
Use the new http client for talking to GitHub in the site app.
Remove RequestResult.
Add support for post (and arbitrary) method requests.
Add a error handler impl for debugging purposes.
Codenarc fix.
Remove RxBackground, relying just on RxRatpack.
Improve the Rx error handling, and add better test coverage.
Expose the response status.
Coerce to string.
Add missing throws.
Imports.
Add Handlers.clientError().
Change ChainAction to implicitly delegate to a Chain in the same way that GroovyChainAction does.
Print the stacktrace to stderr