remove install_requires from setup.py

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
sort the requirements

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
create instructions to install on OSX

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
add generic instructions for installation

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
add link to homebrew

Signed-off-by: Alfredo Deza <alfredo@deza.pe>
Merge pull request #31 from ceph/wip-5941

Instructions for installing teuthology on non-debian-based OSs