Fixing a couple outstanding issues

Issue https://github.com/pandamonia/BlocksKit/issues/133
Added README entry outlining @adamgit's discovery of a missing step for manually building the library.

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Issue https://github.com/pandamonia/BlocksKit/issues/136
The issue first came up as https://github.com/pandamonia/BlocksKit/issues/120, but the fix simply flipped the ordering, which fixes vertical layouts but reverses the expected horizontal ordering of the default cancel button.

UIAlertView seems to change its layout depending on the number of buttons, as well as the button ordering if there is a cancel button title assigned:
* 2 buttons or less, horizontal button layout, cancel button appears first/leftmost with index 0
* 3 buttons or more, vertical button layout, cancel button appears last/bottom with index 0

You could handle both cases by explicitly adding the cancel button as an other button either before or after the other buttons, but I think it's better to simply let UIAlertView handle it, in case some future iOS update changes up the cancel button ordering. (You're also not hacking into the firstOtherButtonIndex that way either)