Tree tab with file list
contentsOfFile:atCommit:
preview pane
Remake preview item when tab is shown
Remove file view
Initially show tree view because of a problem with NSSplitView

If the split view's tab pane isn't the one initially shown, then it comes up with the first pane fully expanded and the second pane collapsed.
Fix icons for files not in workspace
Initially select the head commit

Conflicts:
	Xit/XTHistoryViewController.xib
Change the View toolbar item to Textured Square style
Merge branch 'master' into tree

Conflicts:
	Xit/XTFileListHistoryDataSource.h
	Xit/XTFileListHistoryDataSource.m
	Xit/XTFileViewController.h
	Xit/XTFileViewController.m
Merge fixup
Analyzer fix
View controller owns the context menus
Move context menus to their own xib file
Split out file tab contents
Merge remote-tracking branch 'refs/remotes/github/master' into tree

Conflicts:
	Xit.xcodeproj/project.pbxproj
	Xit/XTFileListHistoryDataSource.m
	Xit/XTHistoryViewController.m
	Xit/XTSideBarOutlineView.m
More modernization
Merge branch 'master' into tree

Conflicts:
	Xit/XTFileListHistoryDataSource.h
	Xit/XTFileListHistoryDataSource.m
	Xit/XTFileViewController.h
	Xit/XTFileViewController.m
Reformat XTPreviewItem
Use RBSplitView for file view

RBSplitView is added as a submodule, a fork with project changes so it compiles with the latest Xcode and links with Xit.