Fix table aliases in joins

Support the intended "table as alias" syntax for table names.
Merge pull request #11 from incredible-labs/table_alias_simpler

Fix table aliases in joins
Merge branch 'master' of github.com:tgriesser/knex

* 'master' of github.com:tgriesser/knex:
  Fix table aliases in joins
Merge branch 'master' into gh-pages

* master:
  Fix table aliases in joins