add a class for forcing something full width

using this for the occasional figure that I want to be full width but
also have the caption stuff, since the default (that I use often) is
figures are 30%

Signed-off-by: Brian S. Stephan <bss@incorporeal.org>

incorporealcms/static/css/base.css

@@ -116,6 +116,10 @@ img {
     max-width: 75% !important;
 }
 
+.full-width {
+    max-width: 100%;
+}
+
 .img-center {
     display: block;
     clear: both;