Update the "go get" path in the README.
Update the "go get" path in the README.

Fixes #12.

FactomProject/snappy-go,sbinet/go-snappy,bmatsuo/snappy,golang/snappy,btcsuite/snappy-go,golang/snappy,monkeybutter/snappy,FactomProject/snappy-go,winlinvip/snappy