Add additional keys to the binary_flag dictionary in the util.data_format file

[timothyareed]

First of all, this is an excellent library and you guys did a great job!

I am pulling some options data from Polygon.IO and then options are labeled as 'CALL' and 'PUT', for this library
they need to be 'c' or 'p', which would require either creating a new DataFrame column or renaming the current column.
which really doesn't add much more time on our side, but can easily be handled in the library. there is a dictionary
"binary_flag" in the util.data_format file that converts the 'c' or 'p' to 1 and -1, I'm proposing adding additional keys to
cover more use cases than just 'c' and 'p'. My current workaround is to simply modify the dictionary after I import the library
as seen below.

import py_vollib_vectorized

Add some key_value pairs to the binary flag dictionary

py_vollib_vectorized.util.data_format.binary_flag['CALL'] = 1
py_vollib_vectorized.util.data_format.binary_flag['PUT'] = -1

[marcdemers]

Hi Timothy,

Can you do a simple PR for this? seems pretty straightforward, just make sure to add a test as well!