Update Gruntfile.js removing pointless reading of customize.html.

I couldn't see a reason to read "customize.html", removed line.
Merge pull request #10841 from DeanMarkTaylor/patch-1

Update Gruntfile.js removing pointless reading of customize.html.
Spelling mistakes in documentation.
Merge pull request #10855 from dan-silver/master

Spelling mistakes in documentation.
Better documentation and optimized examples for grid classes
Update Gruntfile.js fixing undefined jQuery check

The check to see if jQuery was defined as incorrect causing the "Bootstrap requires jQuery" message to only be displayed if jQuery is defined and has a value which equates to `false`.
Added abridged form of 'What's included' docs to README
Merge pull request #10863 from DeanMarkTaylor/patch-2

Update Gruntfile.js fixing undefined jQuery check
rm unnecessary backslashes from jqueryCheck
Moved 'getting started' link out of 'What's included' section in README
Apply help-block class to help text in customize.html
Update qunit dependency
Merge pull request #10869 from ZDroid/patch-2

Update qunit dependency
Remove .ruby-version due to https://github.com/twbs/bootstrap/commit/4f20a29c329aa58919919426cbd2190fabfdb723
Remove "Remove margin on the body" from base css docs

Normalize did that.
also use .col-sm-* in other .form-horizontal example for consistency
use .col-xs-* in "Forms: Column Sizing" docs so more responsive
table contextual classes docs: .col-lg-* => .col-xs-*
remove comma separating the color and the color-stop in -webkit-linear-gradient in the #gradient .vertical mixin.
Merge pull request #10888 from twbs/favor-xs-in-docs

use .col-xs-* in "Forms: Column Sizing" docs so more responsive