Correct indexor -> indexer in code and documentation

This is a breaking change, but it seems better to do it now than later.
As far as I know Go doesn't have a nice way to alias everything
involved, but let me know if you'd like me to do so anyway.
Merge pull request #50 from fractalcat/master

Correct indexor -> indexer in code and documentation
Fix code that triggers go vet errors
Merge pull request #51 from mattoddie/fix-go-vet-errors

Fix code that triggers go vet errors
Merge pull request #49 from araddon/upstream_master

add stops to go routines in bulk indexor when it shuts down
convert BulkIndexor -> bulkIndexer
update unit testing to github.com/bmizerany/assert