Remove the -fno-objc-arc parameter from GTMObjC2Runtime.m,
GTMMethodCheck.m, GTMNSDictionary+URLArguments.m, and
GTMNSString+XML.m.

These all compile correctly in ARC, which is preferable to avoid
sanity-checking them for memory-management errors.
Remove unused GTMLogger.

There was a header-file reference to it, but other than that it's not
being used.
Convert to ARC.
Merge branch 'master' of github.com:tipbit/tidbits