Enabled 802.11 Decryption

Tshark is capable of decrypting traces using the WEP, WPA-PWD, or WPA-PWK standard. All subclasses of pyshark.capture now include keyword arguments decryption_key and encryption_type for doing this in Pyshark.
I think you should probably set these as constants somewhere (i.e. a separate class or module) so that people will be able to know what their options are.