Correct degrees to latitude conversion
added dms2decimal function
added strike_direction function to dtopotools
Convert to using new topotools
Initial commit of topo module containing base topography classes

This includes most of the intended funtionality of a topography class
that is intended to act as a representation of a topography file.  In
particular it will defer calculation of forms of the data until requested
and includes the ability to plot and project unstructured data onto a
structured grid.
several improvements to topotools to allow returning x and y as 1d rather than 2d arrays and to do a better job of plotting topo, especially with imshow option: split into masked arrays for B<0 and B>0 with different colormaps.
Merge remote-tracking branch 'mandli/topotools' into topotools

* mandli/topotools:
  Initial commit of topo module containing base topography classes
  Convert to using new topotools
  Correct degrees to latitude conversion