Add .gitignore for Xcode projects
Add a new Xcode 4.6 project
Add UnitTest++ source to the project
Add a target for TestUnitTest++

TestUnitTest++ is a command-line tool.
Update TestUnitTest++ to use existing code

- Add files from the tests directory
- Add $(SRCROOT)/../../ to the include paths
- Link to libUnitTest++.a
- Remove the TestUnitTest++ group (with main.cpp and TestUnitTest__.1)
  that was automatically generated by Xcode
Merge pull request #40 from chris-frederick/xcode_project

Add Xcode 4.6 project