v1.1 into master

- Test used for trim edges can be adjusted using boolean flags to turn on/off various aspects of the test.
- DQ flags now used to trim edges when determining y-axis range.
- Ratio of flux uncertainties used to trim edges.
- PNG plots are now consistent sizes.
- y-tick labels are now turned off in cases of fluxes being all 0.0.
- Spectral plots are now blue instead of black (except in debug mode).
- Both x- and y-axes now have unit labels.
- Grid lines are now included in large size plots.
- Added option (defaults to False) that uses full value labels for y-axis major tickmarks (includes powers of 10 in scientific notation).
- Added optional test to edge trimming that checks percentiles of flux uncertainties.
- Moved a lot of the common methods into a separate module called specutils.py that reduces code duplication.
- DQ test of edge trimming now avoids DQ=16 flags for STIS, but not for COS.
- There are additional fixes and improvements with this update that are not directly associated with an Issue.