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. 
Only place in code base I find that is:

loomio/lineman/vendor/bower_components/bootstrap/dist/css/bootstrap.css:
loomio/lineman/vendor/bower_components/sass-bootstrap/dist/css/bootstrap.css:

which seems unlikely.
Other place that there might be a lead to was Font-awesome...