hr attributes missing

[bjatkin]

hr tags that have attributes are not keeping those attributes after being compiled.

for example

<hr style="margin: 10px;">

should compile to

<hr style="margin: 10px;">

but instead complies to

<hr>

[bjatkin]

<hr> tags now keep their attributes even after rendering. <br> tags also suffered from the same issue and now maintain their attributes as well. see this commit