Fix for #1579
Added import statements to run examples individually
Fixed 2D and 3D convolution 'None' mode
Changed default of convolve to 'fill'
Canged import order and removed blank lines
Removed redundant complex type check
Added masked array and normalize function tests
Added boundary=None for list test
Fixed masked array handling in convolve_fft
Changed docs to new default behaviour
Merge pull request #1602 from adonath/fix_convolution_none_bug_#1579

Fix convolution none bug #1579
Merge pull request #1644 from mdboom/doctest/convolution

doctest/convolution
Merge pull request #1632 from mdboom/doctest/docs

doctest/docs
Merge pull request #1633 from mdboom/doctest/wcs

doctest/wcs
Include "megabit" and "megabyte" etc., as units.  Fix #1543