transform scan to base link before computing scan angle in turtlebot_calibration

[tfoote]

see this ros.answers.org here:http://answers.ros.org/question/2238/turtlebot-odometryimu-calibration-fails-with

refiling: https://kforge.ros.org/turtlebot/trac/ticket/67

[bit-pirate]

Tully, please assign new issues to the Hydro milestone, if you think we need to fix them for the release or TODO otherwise. Thanks!