By default, use a 100% width embed frame

git-svn-id: https://plugins.svn.wordpress.org/vanilla-pdf-embed/trunk@856625 b8457f37-d9ea-0310-8a92-e5e31aec5664
Expand readme for v0.0.4

git-svn-id: https://plugins.svn.wordpress.org/vanilla-pdf-embed/trunk@856626 b8457f37-d9ea-0310-8a92-e5e31aec5664
Provide a null default for $h in vpdfe_pdf_embed_html

Thanks to firedog341 for the bug report.

git-svn-id: https://plugins.svn.wordpress.org/vanilla-pdf-embed/trunk@856809 b8457f37-d9ea-0310-8a92-e5e31aec5664
Set a default height of 500em

git-svn-id: https://plugins.svn.wordpress.org/vanilla-pdf-embed/trunk@858107 b8457f37-d9ea-0310-8a92-e5e31aec5664