ContinuumIO/blaze — pull request #373 by mrocklin (2014-07-03 18:48:18+00:00)
Title: expr: Join automatically selects all shared columns

```Python
t = TableSymbol('t', '{name: string, amount: int}')
s = TableSymbol('t', '{name: string, id: int}')
assert Join(t, s) == Join(t, s, 'name', 'name')
```