fixed typo in gemfile doc
Merge pull request #425 from thedamfr/patch-1

fixed typo in gemfile doc
added documentation, how to use variables

couldn't understand how to modify the bootstrap variables. Added an example where we redefined a variable value. And define a variable in terms of another variable.
Merge pull request #432 from morenoh149/patch-1

added documentation, how to use variables
Merge remote-tracking branch 'upstream/3' into 3.0.0-wellnessfx
add float:left for full width grids (col-xx-12) as it forces wrapping when necessary