release pasteboard items et al since MMTabPasteboardItem retains UI objects

MMTabPasteboardItem retains the MMTabBarView (sourceTabBar) which
prevents the object from being released. Since the MMTabBarView also
retains the NSTabView and any NSTabViewItems this quickly locks up a
number of other objects such that when the window is closed these still
remain.
Revert "release pasteboard items et al since MMTabPasteboardItem retains UI objects"

This reverts commit f343b9cc97d631f34be4dde3c7c296f23132f409.
Better solution to the pasteboard hanging on to UI objects
merge upstream changes
Merge pull request #9 from nivekkagicom/master

Merged. Sorry for the delay. Thank you!