Count RE: as a reply header, just like Re: so we don't chain Re: RE: RE: subject when replying.  Fixes Bitmessage/PyBitmessage #382
add installation

people will likely go straight to installation page, so I added to readme.
Merge pull request #410 from Atheros1/master

added some more error handling
Have OSX check run before we import classes and error out
Merge pull request #412 from grant-olson/move_osx_python_check

App fails with system python before OSX system check
Merge pull request #406 from chovy/patch-1

add installation
Merge pull request #404 from grant-olson/detect_RE_as_reply

Count RE: as a reply header, just like Re: so we don't chain Re: RE: RE:...
show number of each message type processed in the API command clientStatus