Quick fix for PDFs not rendering

Add a short (50 ms) delay before inserting the CSS link tag to work
around a Chrome bug preventing PDFs from rendering. This is a band-aid I
need to fix with a better strategy.
Bump version to 0.6.1
Merge branch 'hotfix'

Changelog for release 0.6.1:
  * Quick fix for issue #65 - "Cannot open PDFs."