Allow cli plugin to take query params
Logs: add log piping support to the cli plugin

* If a build comes in with build._control.tail_log == true, log streams
  will be made available (by the git-plugin) at build._control.logs
  once the build has started.

* The _control property has been added to builds to allow plugins to
  pass around data that isn't really intended to be serialized or isn't
  about the build itself.

* If the tail_log query param is set when submitting builds using the
  HTTP endpoint, the response will block until the build is started.
  The respone will contain the serialized build on the first line and
  then the log will be streamed.
CLI: add blocking tail option to cli

With --tail the 'build' command will now block until the build starts.
Then, it will print the JSON build, and tail the log file.
Refactor an if block to DRY up code.
Merge blocking-cli (#29) into master

Add blocking and log-tailing option to CLI

The CLI now supports the --tail option which will cause the client to
block until the builds starts then tail the log.

The log is streamed over the http response to the reuuest that created
the build.

Conflicts:
	bin/cimpler
	plugins/git-build.js
	test/cli.test.js