README has out of date instructions for OSX

[hamishdickson]

The README says users should run the command

gem install jekyll

OSX has gone rootless in El Capitan, so instead this should actually be (for OSX anyway)

sudo gem install -n /usr/local/bin/ jekyll

see http://stackoverflow.com/questions/31567029/how-can-i-install-jekyll-on-osx-10-11 for more details

I believe the part about updating ruby gems is still correct however

[SethTisue]

@soc and I have attempted to address this in #361 by recommending that gems not be installed globally, but that Bundler be used instead.

[hamishdickson]

@SethTisue that sounds sensible, let me know if you need me to do anything

[soc]

"rootless" sounds a lot like "cloud". :-)

[SethTisue]

new attempt to address this: #373

[SethTisue]

#373 was merged, see also #375. thanks for calling this to our attention.