ENH: Add conda support

This PR provides 2 changes, it:
1. changes travis to use conda which brings down the build process from ~50 mins to >10 mins. For this I uploaded compiled versions of ta-lib and logbook to my channel: https://binstar.org/twiecki
2. provides conda build files to create binary packages of (i) dependencies not already supported by anaconda and (ii) zipline itself. Currently I have only uploaded linux 64bit versions but it should be possible to create osx and windows binaries as well. This should make installation of zipline for users much much easier.