changed .hms and .dms attributes to output a named tuple instead of a regular tuple
fixed tests to match new dms/hms
fix docstrings to reflect namedtuple dms/hms
added absdms attribute to Angle
Update changelog
Clarified in docstrings that named tuples were being returned as suggested by @cdeil
Add a negative examples case to the docs as suggested by @cdeil
Simply absolute value-taking for dms as suggested by @mhvk
Changed `absdms` to `signed_dms` as suggested by @mhvk
Removed remaining mentions of `absdms` as pointed out by @cdeil
Adjusted examples to only do negative angles where there's a point (suggested by @mhvk)
changed named tuples for hms/dms to lower-case convention at the suggestion of @astrofrog
Merge pull request #1988 from eteq/hmsdmsnamedtuple

Make hms/dms namedtuples and add `signed_dms`