Add github.com/syndtr/goleveldb/leveldb

To be used as a sorted.KeyValue.
Upstrem version is 9bca75c48d6c31becfbb127702b425e7226052e3

I've removed some tests which would require github.com/onsi/gingko &Co.

Change-Id: I0ee50ca7d10a882b1c5ff73a81e52006e3554c4d
Add sorted/leveldb.

Change-Id: I0d46a86b33d2e1d2992d8a41f08979eb21aaddbb