Renamed the zipline directory to alephnull so that any changes are considered part of AlephNull and not some zipline patch.
Changed all references to the "zipline" package to the "alephnull"
package, including modifying setup and .gitignore files to react to this
change. Note that some zipline naming conventions have not been addressed
(i.e. there are still zp_math imports, etc.) and references to zipline in
docstrings have not been changed.