Removed backView & added podspec

Completely removed backView because we already have backgroundView in
UITableViewCell and can use it as revealed view. And using backView as
it was used interfered with selectedBackgroundView, so cell contentView
always becomes transparent and showed contents of backView. This is
fixed now.
Merge pull request #15 from xzeror/master

Removed backView because of bug: cell contentView becomes transparent and shows backView behind.