Adding channels for reporting logs, status, and error

This release updates the runner's RunBuild() function to return three channels. The first receives log entries and the second receives status updates with useful data (currently just in the form of map[string]interface{}). The third receives only one value, error or nil - this is the return value and also indicates that the overall build has completed.

In addition to RunBuild(), there is now a RunBuildSynchronously() function that uses a default logger and returns error/nil after the build is complete. This method also serves as a good example of how to use the channels returned by RunBuild() in another context