Using stirngToIdentifier on hash keys in select() for doing aliases

This fixes `dataset.select({table__column: "aliasName"}).sql` -> `SELECT table__column AS aliasName FROM test`.  

I realize there are other ways to accomplish this, in fact I ended up using "table__column___alias" for what I was doing, but this is the first thing I tried for some reason. Fixing just in case others try this method as well.