Local changes, Increased functionality in obtaining builds, and ability ...

Added increased functionality in obtaining builds and ability to print changeset class.

get_builds_in_time_range will return all builds that occurred for a job between the specified
start and end times.

has_changes will return whether or not there is anything in the changeset node.
__str__ will format a string appropriately so the class can be printed.


Removed superfluous print statement that spoils usage of get_last_failed_build.