Patches for Yosemite

This gets rippled going on Yosemite.

After upgrading you have to re-install command-line tools prior to building:
$ xcode-select --install

Tested on both Mavericks and Yosemite.  Passes Travis.
@josh-ripple @niq
````
scons: Reading SConscript files ...
AttributeError: 'list' object has no attribute 'join':
  File "/Users/howardhinnant/Development/rippled/SConstruct", line 57:
    import Beast
  File "src/beast/site_scons/Beast.py", line 92:
    system = __System()
  File "src/beast/site_scons/Beast.py", line 65:
    self.__display = '%s %s' % (self.name, parts.join('.'))

````