Fixed bug in aggregation routine

This bug was leading to very large UH ordinates and the selection of fill values during convolution
The routine now checks a mask created from both the sum of the UHs and the fractions to confirm that
all points in the output file correspond to acual grid points.
Combined basin_agg.py and remap_stations.py into remap_UH.py

This change allows for the use of a single script to remap and aggregate high resolution grids
This change simply added an if statement to the basin_agg routine so that the aggregation step is
skipped if the --agg flag is not called.
A entirely new convolve.py, this is essentially a new program which replaces the previous
Initial commit of make_flat_uhs.py
Change to remap_UH.  Now writes out outlet grid location in grid coordinates.

Uses cKDtree to find the indicies of each outlet point.  These coordinates are
saved as global attributes in the output netcdf.  This facilitates easy allocation
of streamflow during convolution.
initial commit of coup_conv.py, a mock coupled model implementation of the RVIC model.
sample coupled model configuration file