Bias-Tee option in rtl_sdr utility

[darksidelemm]

It looks like the enable bias-tee option has been in added in every command-line utility except for rtl_sdr! Is there a reason for this? Just an oversight?
I find the rtl_sdr utility very useful as a way of easily extracting samples out of a RTLSDR for piping into other processes.

[erikarn]

I've added rtl_biast as a command line in a pull request (#55).