Mac port of rez + tweak to init.csh file.

Cover issues #27, #26, #25, #24, #23.
Fix https://github.com/nerdvegas/rez/issues/29
Allow Darwin to pretty print error in the console
The examples/demo runs fully on the Mac !

A good step towarad #24
rez is taken on osx so change to use rez- variants

cf #30
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Fix typo in configure.sh ...
Refactor + make python version detection works with version < 2.7
Remove a dependency on GNU sed / replaced with python code
Remove debugging code :)
Fix indent on configure and install (4 spaces indent)
Fix indents (take 2)
Mac - rezpy cannot be a symlink to /usr/bin/python
Adding instruction to get setup on OSX
Adding a markdown formatted README for github.
Tweak the README.markdown
Merge remote-tracking branch 'bsergean/master' into merge_osx

Conflicts:
	bin/_set-rez-env
	bin/rez-env