use a smarter regex when escaping html entities (<>&): avoid escaping valid html character entities like &amp;
comment explaining the regex and unit test
fix unit test, partially reverting fc86ca0ca9df73934ffc09c4539b6fe8e465acdf
Merge pull request #1013 from unicolet/pullrequest/rendercontext_escapehtml

use a smarter regex when escaping html entities (<>&)