add BarFeed support for pandas, generic sequences

[tmkontra]

builds off of #107 by @flipdazed and suggestions by @gbeced

• barfeed.listfeed
  • list of dicts requiring standard column naming scheme
  • sequence items are passed through csvfeed.GenericRowParser
• barfeed.pandasfeed
  • maps dataframe rows directly to bar.BasicBar via DataFrame.apply

[tmkontra]

TODO: Planning to add test cases.

Was not clear how to run tests locally, it looks like Docker might be the best way? Spin up container and manually run test cases?

There appears to be a number of integration dependencies (twitter, quandl, etc), so relying on this repository's travis hook seemed the quickest way.