add a sheet block category on NSApplication
style fixes
use rbl prefix instead of underscore
single-line method declarations
Popover window should act like a key window.
add header, fix all the things

- Setting the associated object onto the passed-in window.
- Stray "&"s
rework -prepareForReuse

It is now called when the cell has actually been removed from the
superview. However, it is also called when the cell is initially
created and has no superview, so this has been noted in the comments.
whoops!
Move RBLPopoverWindow's implementation down to where others are.
Merge pull request #41 from luosheng/popover-acting-like-key

Popover window should act like a key window.
remove linebreaks
return code type
Merge pull request #40 from jwilling/master

Add support for a block-based sheet handler
Merge branch 'master' into fix-tablecellview
lol newline
extend comment
Merge pull request #42 from jwilling/fix-tablecellview

Modify NSTableCellView a bit.
Implement clipsToBounds on RBLView
Make memory management of RBLView's opaque and flipped properties explicit
Note that RBLView's clipsToBounds passes through to its layer's maskToBounds property