New features
* Refactored bbi functions into a cdef class `BBIFile` obtained with `bbi.open()` (13). The function API is preserved.
* `BBIFile` adds support to read and parse a bigBed's AutoSql schema definition
* AutoSql scalar types are mapped to numpy/pandas dtypes
* AutoSql listed/array types or other exotic types are treated as regular strings
API changes
* `fetch_intervals` takes an additional `iterator` parameter. If True, it will return an interval iterator (of tuples) with the same behavior as in v0.2. If False, returns a dataframe with columns correctly parsed using the AutoSql schema. The class method returns a dataframe by default, and the function returns the iterator by default to preserve existing behavior.
* Python 2.7 support has been dropped.