Use constants for repeating values.  Fixes an issue where the height of the meta view was miscalculated when the cell was configured.
Fixes an issue where the reblog button's appearance was not updated after reblogging.
Fixes an issue where the post's isReblogged property was not updated after reblogging.
Disable the reblog button for posts that have already been reblogged.  This prevents a user reblogging to multiple blogs, (argueably an edge case) but matches the current behavior of the .com reader.