Refactor EditorDiffMargin.UpdateDiffDimensions to simplify visibility handling
Remove unnecessary code duplication
Duplicate UpdateDiffDimensionsImpl in preparation for separate handling of removed blocks
Simplified code for handling "normal" hunks
Simplified code for handling "deleted" hunks (fixes #44)
Fix incorrect handling of submodules
Perform required argument check before calling Repository.IsValid
Do not create custom margins for files not located in a Git repository
Add support for Visual Studio 14 CTP
Merge pull request #50 from sharwell/play-nice

Play nice with other source control providers
Merge pull request #51 from sharwell/submodules

Fix incorrect handling of submodules
Merge pull request #48 from sharwell/fix-44

Improved editor diff positioning
Merge pull request #55 from sharwell/vs14ctp

Add support for Visual Studio 14 CTP
Expose IGitCommands through MEF instead of direct construction
Improved documentation for and simpler implementation of IsGitRepository
Create separate documented methods GetGitRepository and GetGitWorkingCopy; use where appropriate