Launches image picker controller with image picker scrolled to bottom
Stops showing the partially loaded photos, since that causes a jarring jump to the bottom when the full photo list loads
Makes the picker snappy like regular iOS Photos by preloading the last ~25 images before loading the rest
Adds a comment explaining what is going on
AssetTablePicker behaves like iOS Photos: loads scrolled to the bottom and loads quickly
* Loads the picker so that the tableview is initially scrolled to the bottom
* Loads the last ~25 images in the library first, so the picker screen comes up
  snappily even for very large libraries. This makes the image picker behave
  just like iOS Photos, as far as I can tell.
Resolves crash when you press done before all the photos have loaded
Merge branch 'assettablepicker-behaves-like-iOS-photos'

Conflicts:
	Classes/ELCAssetTablePicker.m
Further attempt to fix this crash and resolve concurrency problems with loading asset library in background
load the first 100 rather than first 25 photos
AssetTablePicker behaves like iOS Photos: loads scrolled to the bottom and loads quickly
* Loads the picker so that the tableview is initially scrolled to the bottom
* Loads the last ~25 images in the library first, so the picker screen comes up
  snappily even for very large libraries. This makes the image picker behave
  just like iOS Photos, as far as I can tell.
Resolves crash when you press done before all the photos have loaded
load the first 100 rather than first 25 photos
Includes the changes to make the picker load the first 100 images,
and also resolves problem of crashing if you pick images before the whole
gallery has loaded
Merge branch 'assettablepicker-behaves-like-iOS-photos'

Conflicts:
	Classes/ELCAssetTablePicker.m
Takes processing of assets off main thread so picker is more responsive when done button is pressed
Handle case when there are zero photos
Changes willFinish callback on ELCImagePickerController to also include how many media items have been selected
Makes the processing of photos more sequential to reduce memory warnings
moves everything onto backgorund thread in ELCImagePickerController
Only show albums which have at least one photo for choosing