0.7.3 has breaking changes to 0.7.2

Hello,
Seems like patch versions were used for backward incompatible changes.
Example:

I have the following function that works fine in 0.7.2:

```
def snappy_decompress_stream(in_file, out_file):
decompress_func, read_chunk = snappy_formats.get_decompress_function(snappy_formats.DEFAULT_FORMAT, in_file)
decompress_func(in_file, out_file, start_chunk=read_chunk)
```

The above function doesn't work in 0.7.3
There is no `snappy_formats.DEFAULT_FORMAT` anymore. Looking at the unit tests, it seems `get_decompress_function`is not used and instead a `snappy.StreamCompressor` is introduced.

I'm a little confused about a patch breaking all the above!