New development error page styles

Closes #448
Some more convenience to with.
Some tweaks to URL building.
Add convenience for get requests with no configuration.
Fix escaping issue with path segment patterns.
Merge pull request #463 from robzienert/new-error-styles

New development error page styles
Fix GitHub API requests for site.
Provide a throttle for generic operations.

Closes #449.
Upgrade to latest RxJava.
Fix problems with defer(), and add extra promise operations useful for diagnostics.
Add a mechanism for dumping out current executions.
Merge remote-tracking branch 'upstream/master'