BUG: Binary literals' type is not inferred

[cpcloud]

Is there any reason not to infer bytes literals as binary?

>>> import ibis
>>> ibis.literal(b"abc")
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/cloud/src/ibis/ibis/expr/types.py", line 1288, in literal
    raise TypeError(
TypeError: The datatype of value b'abc' cannot be inferred, try passing it explicitly with the `type` keyword.

[jreback]

this seems reasonable