Resource fixes

1.  Can pass dshape and schema kwargs from Table to resource as in 

        Table('foo.csv', schema='...')

2.  resource('/path/to/*.csv') now enforces that the schema of the first item should be the same on all of the items.
hm i guess i don't see why have this on globbed resources then, until we can decide how to handle the multiple schema (maybe same names, but different types) case