Misc cleanups and docs

Some fixes/cleanups:
1) Renamed 'self' reciever names, as it's doesn't sound native for Go.
2) Changed Load() to LoadFromFile() in example in Readme.
3) Added simple functions descriptions to be used in godoc.
4) Added example function for godoc.
5) Hidden Scanner interface from being public (renamed to scanner)
6) Also I was about to rename Queryer to Querier (it sounds more native), but then found Queryer name in database/sql/driver and decided to left as is.