draw_grid improvements
Time-dependent assumptions when missing metadata (distance to Sun and apparent solar radius)
PEP8 indention fixes
Changelog entry for draw_grid changes
Changed print to warnings.warn_explicit
Merge pull request #1048 from ayshih/draw_grid

[Review]: Fixing `draw_grid`
Added same behavior for carrington_longitude and heliographic_latitude
Changed import of sunpy.sun functions
Merge pull request #1047 from ayshih/metadata

Alternate approach to missing location-related metadata