Xunique

Fixed bugs and new features:
- 25 adding warning output to ask for removing reduntant sections manually; before only the line with unused uuid would be removed, that will make project file cannot open.
- 28 add Python 3 compatibility

Thanks heni for the python3 support contribution

Now you can use xUnique in terminal directly like `xunique -h`, no more python prefixes.

Fixed bugs and new features:
- 21 add command line script in PATH, so you can use `xunique` as a common command in terminal.
- 19 add advices for Cocoapods users
- 22 fixes typos in README
- 22 fixes pep8 style issues in xUnique

Thanks schwa for the contributions in 21 22
Thanks Julyyq for the suggestions in 19

fixes 18: make CopyFiles and ShellScript build phase more unique

Change the way of generating MD5:
**This will make all MD5 in your project file change! so if you collaborate with others in vcs, make sure that you all update to 4.1.0 via `pip install --upgrade xUnique`**

Fixed bugs and new features:
- add more versbose output in `-v` mode
- refactored MD5 generating rule, changed `path` generating method: now it is surrounded with an `isa` type and `[]`

Now I have uploaded _xUnique_ to PyPI.
You can install it with one command: `pip install xUnique`, and then use it via `python2 -mxUnique [options] path_to_xcodeproj/or_pbxproj`

Fixed bugs and new features:
- find one missing `isa` type: `PBXBuildRule` and add support for it
- remove unused children in reference and group type
- print out removed lines when uniquifying and sorting
- change README format to reStructedText
- add support for PyPi
and I have already uploaded this new version to PyPI

This is the first production release that can be used in production environment.
This version is now used in ongoing Taobao Trip v5 version of Alibaba Trip BU . The project consists of ~25 Xcode sub-projects. And now xUnique works like a charm in the whole project.
Cheers to all the developers in Alibaba Trip iOS Developer team to gave suggestions and send bugged project file to help improving xUnique.

New features
- Two new argument options:
- add `-c` option: When project file was modified, xUnique quit with non-zero status. Without this option, the status code would be zero if so. This option is usually used in Git hook to submit xUnique result combined with your original new commit.
- add `-p` option: Sort `PBXFileReference` and `PBXBuildFile` sections in project file ordered by file names. before v4.0.0，it was default in `-s` option and cannot be turned off. Now, without this option, xUnique will sort these two types by MD5 digests, the same as Xcode does.
- New features:
- now xUnique will also remove duplicate items in `PBXBuildFile`, `PBXFileReference`, `children` and `files`
- colorful xUnique output:
- RED: fatal error
- YELLOW: warning
- GREEN: pass
- add more output when xUnique modified project file
- rewrote `how to use` section in README: now added a recommended method to use xUnique, with a gif animation demo.
- Bug fix:
- Fix bug 2
- Fix bug 3
- Fix bug 4
- Fix bug 5
- Fix bug 6
- Fix bug 7
- Fix bug 8
- Fix bug 9
- Fix bug 10
- Fix bug 11
- As Mac OS X is only case preserving, now use PBXProject name found in project file as the root node path. Do not use `xcodeproj` name from file path any more.