store coordinate angles internally as _latangle/_lonangle instead of subclass-specific
Added getitem for coordinates to allow indexing

closes #1508
Added test of array indexing of coordinates
add test to make sure equinox is passed-through
Change coordinate matching to use coordinates __getitem__
Clarified matching example with inclusion of indexing use
Add mention of getitem work in CHANGES.rst
added info to whatsnew
Add example of indexing coordiantes to getting started
Merge pull request #1615 from eteq/coordinates-indexing

Coordinates indexing