Creating Buffer directly from pointer/length

[Randy Zwitch]

Within OmniSci (MapD), we have the following code that takes a pointer 
and length and reads to a NumPy array before calling py_buffer:

https://github.com/omnisci/pymapd/blob/master/pymapd/shm.pyx#L31-L52
Is it possible to eliminate the NumPy step and go directly do an Arrow 
buffer? There is both a concern that we're doing an unnecessary memory 
copy, as well as wanting to defer to the Arrow way of doing things as 
much as possible rather than having our own shims like these.