No waterfall support for filterbank files

[MilesCranmer]

Some problems come up when you try to read a filterbank file into waterfaller.py. It does not seem as though there is support for the format, despite the description on the file preamble (e.g., it isn't even possible to get past the if statement from line 281 onwards ).

I can add support on my fork and then submit a pull request. Should I wait for Chitrang's pull request to be finalized before working on this?

[MilesCranmer]

Oops, I just read #65. @pscholz have you started to work on the filterbank support yet? I have some code that I wrote for a different software (includes filterbank support) that I can reconfigure to what you have.