Removed two_arg_log function, since it isn't being used.  Also, changed log and log10 to use scipy.log and scipy.log10 so that logs of negative numbers can be handled.
Removed two_arg_log function, since it isn't being used.  Also, changed log and log10 to use scipy.log and scipy.log10 so that logs of negative numbers can be handled.

GutenkunstLab/SloppyCell,GutenkunstLab/SloppyCell