T-Mobile is currently offering the HTC Sensation 4G free through tomorrow, May 3rd.  The web-only offer gives you an instant $199 off the phone making it completely free with a new two-year agreement. The Sensation 4G ships with a 1.2GHz dual-core Qualcomm processor, 768MB of RAM, a 4.3″ qHD screen, and the ability to shoot…