Move search into its own file.
Fix a bug where only the last term would be searched for.
* Lowercase the search terms
* Had one too many %s in the search tree builder
Change bigFile.processChunk to work in bytes, so it can convert them to runes.

This is necessary because the DB files are in ASCII not UTF8, and Go will not
decode them properly otherwise.

Unfortunately this moves the buf allocation in readFile to inside the loop,
which is a performance hit ~1s.
Gofmt