Sketch API for resample_images function

The job of this function will be to resample images so that the wedge is
along the x-axis.
Create TargetWCS class for resampling

The TargetWCS class computes the FITS WCS values appropriate for the
resampled images so that the wedge axis is along the x-axis.
TargetWCS.write_fits() method
Change resample_images API to include wedge length+height
Integrate TargetWCS into resample_images function
Integrate skyoffset.MosaicResampler with resample module
Create WedgeBins class to def geometry of bins

Assumes the image has been rotated so PA is along positive x-axis.
Can create sets of bins that increase rightward (default) or leftward
from the center pixel.
Make WedgeBins iterable
Implement measure_image() function

This function takes a FITS image and WedgeBin instance and measures the level
and standard deviation in each bin. Returns a record array giving the
radius and levels along the profile