Merge pull request #14098 from Amit-Thawait/master

Typo fix for unscope [ci skip]
Merge pull request #14099 from robertomiranda/render-text-2-plain

Update Docs in favor to use render plain instead of text option
Fix render plain docs example in AM::Base

The errors were introduced in e220a34e39
Merge pull request #14120 from gregmolnar/guides

change 'assert !' to 'assert_not' in guides [ci skip]
Merge pull request #14131 from kuldeepaggarwal/upgrade-rails-version

update guides to new version of rails 3.2.x, i.e. 3.2.17 [skip ci]