When using bundler, jekyll serve --watch results in an error:

WARN: Unresolved specs during Gem::Specification.reset:
redcarpet (~> 3.1)
WARN: Clearing out unresolved specs.
Please report a bug if this causes problems.
/usr/local/lib/ruby/gems/2.1.0/gems/jekyll-2.5.3/bin/jekyll:21:in block in <top (required)>': cannot load such file -- jekyll/version (LoadError) from /usr/local/lib/ruby/gems/2.1.0/gems/mercenary-0.3.5/lib/mercenary.rb:18:inprogram'
from /usr/local/lib/ruby/gems/2.1.0/gems/jekyll-2.5.3/bin/jekyll:20:in <top (required)>' from /usr/local/bin/jekyll:23:inload'
from /usr/local/bin/jekyll:23:in `

The correct command to run a local server is bundle exec jekyll serve. Just thought you might want to update the readme for people new to bundler.

Thanks for the great tool!