Update gitignore

Exclude OS X .DS_Store files and test spheres until suitable
replacements can be created.
Handle partial spheres without failing horribly
A white background is wrong
More work to handle partial images better (in progress)
Attempt to figure out the proper start position
Those names were confusing me
Define a mid-point and use that as the baseline for auto-panning
Not going to pursue the Chrome extension
Keeping a partial photosphere in frame (min/max longitudes)
Images, fix for north-facing camera

Suitable (although not perfect) demo images.
Fix for not correctly calculating max north latitude (and thus not
displaying images' tops when requested)
More work at initial placement and tidying
Proper start point calculation finally
Still not cracked it