Convert the xibs to Xcode 5.1 format.
The SUUpdateAlert wasn’t migrated in this commit because of the autolayout branch.
Migrate the SUUpdateAlert xibs to Xcode 5.
Updated README
Merge pull request #335 from pornel/master

Finish moving all informal protocols to formal protocols.
Merge pull request #39 from pornel/Xcode5xibs

Migrate xibs to Xcode 5
If the downloaded update fails the code signing check, log out some more detailed information to help with diagnosing the problem.
Fixed potential CFRelease of NULL, code style fixes
zh-CN translate "Learn More" button
Fix memory leak.
Xcode project: set organization name and class prefix.
Silence CSSM warnings in SUDSAVerifier.
Silence sign conversion warnings in third party code.
Remove trailing semicolons.
Add __attribute__((noreturn)) to hint for compiler optimizations.

exit() logically guarantees the method will never return;
this attribute allows the compiler to optimize for this case.
Remove unused exception parameters.
Replace id with specific types where appropriate.
BOOL is a signed char; make sure it’s only ever YES or NO, not in [2, 255].
Don’t compare floating point values with ==
Add missing extern declaration.
Make string constants static as they are not used outside the translation unit.