remove incomplete mysql and cockroachdb support

Documentation/storage.md

glide.lock

glide.yaml

storage/sql/sql.go

storage/sql/standup.sh

vendor/github.com/cockroachdb/cockroach-go/LICENSE

vendor/github.com/cockroachdb/cockroach-go/crdb/tx.go

vendor/github.com/go-sql-driver/mysql/LICENSE

vendor/github.com/go-sql-driver/mysql/appengine.go

vendor/github.com/go-sql-driver/mysql/buffer.go

vendor/github.com/go-sql-driver/mysql/collations.go

vendor/github.com/go-sql-driver/mysql/connection.go

vendor/github.com/go-sql-driver/mysql/const.go

vendor/github.com/go-sql-driver/mysql/driver.go

vendor/github.com/go-sql-driver/mysql/dsn.go

vendor/github.com/go-sql-driver/mysql/errors.go

vendor/github.com/go-sql-driver/mysql/infile.go

vendor/github.com/go-sql-driver/mysql/packets.go

vendor/github.com/go-sql-driver/mysql/result.go

vendor/github.com/go-sql-driver/mysql/rows.go