only setting OHATTRIBUTEDLABEL_WARN_ABOUT_KNOWN_ISSUES and OHATTRIBUTEDLABEL_WARN_ABOUT_OLD_API if they where not defined otherwise before.
Removed warnings about UITextAlignment & UILineBreakMode in Xcode5 / iOS7 SDK
See #154
Fixed typo (for #154 again)
Properly removed #warning when using OHAttributedLabel with CocoaPods
(removed the #define added in the pch by the podspec and adapted the test condition instead)
Fixed warnings for Xcode5 (deprecated UITextAlignment / UILineBreakMode) — closes #154
Merge pull request #143 from 343max/makeWarningsOptional

Only setting OHATTRIBUTEDLABEL_WARN_ABOUT_KNOWN_ISSUES and OHATTRIBUT… …
…EDLABEL_WARN_ABOUT_OLD_API if they where not defined otherwise before.
Fixed iOS5 crash (because I was using new API not available before iOS6)