more better indexing

• require UTF8 files -- "nice" error checking required scanning the whole file, which was resource intensive, now we just preflight that with a script (script/makeutf8.sh), rather than doing lots of error checking on import
• no longer index at app startup:
  • rake import recommended
  • experimental web ui export INDEX_APP=enable to access /index/reindex
• performance improvements for indexing
• some code refactoring to improve readability

Fewer Spurious Errors

• Move from Travis to Circle CI
• Update New Relic gem, so as to use the new Error Analytics features
• Upgrade puma to 2.15.3 so it builds on OS X 10.11 OK
• Fix various errors we're seeing in NewRelic:
  • better zip/distance error reporting (fixes #265 and #266)
  • stats on nested fields no longer throw a stack trace, but doesn't yet give correct result (#276)
• Remove obsolete RunRailsCops rubocop directive
• Document location field (#227)