Add class for system profile.
Add methods to track usage time.
Refactor interface to use singleton.
Merge remote-tracking branch 'origin/develop' into feature/SystemProfile
Add parameter for bundle to methods for system and usage data.
Update project with recommended settings for Xcode 4.6
Fix compiler warning in header file
Update nib to fix compiler warning
Update copyright
Make sure showMainApplicationWindow delegate is only invoked once ever

Fixes #8 (https://github.com/bitstadium/HockeySDK-Mac/issues/8)
Clarify setup, correct a couple typo/tag problems
Merge remote-tracking branch 'origin/feature/SystemProfile' into develop
Move IOKit framework in correct Xcode project folder
Fix typo in property definition
More optional debug log messages
Added documentation on Sparkle usage and some more minor improvements
Improve usage time tracking and make it more error resistant
Actually reset the usage time when saving it
Add missing links to sandbox ready sparkle fork to documentation
Add example code to the documentation for startUsage and stopUsage with appDelegate
Fix formatting errors in documentation