Add variants of SQL types

Came across this issue where I was trying to use blaze on a sqlalchemy table I created with a column made with the `sa.Numeric` type. It yielded an error, and when I investigated saw that blaze looks for `sa.NUMERIC` instead. Not quite sure if there is a difference, but if not we should add the lower case to the type checking.

```
t = sa.Table(name, meta, sa.Column('foo', sa.Numeric(precision=18), primary_key=True))
bz.data(t)
```