travis: Switch from raring to saucy

raring has been removed from the mirrors and was no longer supported
Merge pull request #872 from rleigh-dundee/travis-saucy-dev50

travis: Switch from raring to saucy
Slightly expanded re-indexing intro
New CLI reindex commands
Clarify *when* to re-index
Migrate troubleshooting text to search.txt
Add note about fewer results during indexing
Fix indent in bullets
Clarify that FileAnnotations are not under 'annotation:'