Install commandT for macvim

1. download commandT vimball file

2. open vimball and run so %

3. move the extracted file to bundle folder if needed

4. run CommandT in vim, doesn't work, saying cannot find c extension

5. run ruby extconf.rb under vimfiles/bundle/commandT/ruby

6. failed, and saying cannot find ruby header files

7. install xcode commandline tool

8. restart (may not needed)

9. do step5

10. all good, run make

11. do 4, all good.

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Feng