fix blockquote style

Users reported problems with markdown blockquotes being out of control large.

investigated and found the style was `font-size: inherit`  
and that it was inheriting `font-size: 17.5px;` from .. not sure. 

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for anyone who cares to investigate: 

Only place in code base I find that were

- loomio/lineman/vendor/bower_components/bootstrap/dist/css/bootstrap.css:
- loomio/lineman/vendor/bower_components/sass-bootstrap/dist/css/bootstrap.css:

Other place that there might be a lead to was Font-awesome...