Test update
Added link to my talk at Portland Big Data User Group.

+ Corrected base URL for Apache GitHub pages (_config.yml).
+ Updated Drill's GitHub URL (menu.html).
+ Spelling fixes.
+ CRLF => LF, trimmed trailing space.
+ Fixed extraneous DIV tags (overview.html).
+ Removed TABS, restructured nested element with 2 spaces.
Drill top-level project announcement updates
Merge remote-tracking branch 'upstream/gh-pages' into gh-pages