Rename userAgent -> userAgentString

Apparently Apple doesn't like it when asi-http synthesizes userAgent.

https://github.com/pokeb/asi-http-request/issues/309
Merge pull request #310 from erikchen/user_agent_fix

Rename userAgent -> userAgentString
Fix the userAgent test case.

#309
Merge pull request #312 from skabber/master

Update the test case due to the userAgent to userAgentString change.
fix 6 warnings in xCode 4.3.3 and xCode4.5 DP1
Fixed some format specifiers
Merge pull request #337 from MihaiDamian/master

Minor fixes for warnings reported by static analyzer
Merge branch 'master' of https://github.com/OpenFibers/asi-http-request into OpenFibers-master

Conflicts (already fixed so discarded these):
	Classes/ASIDataCompressor.m
	Classes/ASIDataDecompressor.m
(and changed ASIS3BucketRequest.m to avoid the need to cast)