V0.6.3: Bug fixes and more polish

My previous release was a bit rushed, so these changes are more to add a bit polish to new features that I previously announced.

• POSHTUI can now handle absense of digest files on local machines (e.g. ruby.json)
• I have mistakenly used git tags for ruby as folder names e.g. v3_0_0, but entire application expects v3.0.0. All docsets have been fixed and reupload!
• My docset publishing system now know how to purge older version of edge of CDN automatically now (less button to push!)