Add ability to read file object

[simonghrt]

A function read_file_object has been added in order to be able to directly read a file object (useful for many usecases)

[simonghrt]

This PR is based on [https://github.com/atlanhq/camelot/pull/331](this one) as it's the same use case. I added a test and modified the code in a simpler way (and following PEP8 guidelines). I've read your previous comment about the read_file_obj in the main interface but I didn't see any other alternatives. Let me know if you wish any modifications

[yeus]

just realizing this is a somewhat old? repository?

@simonghrt if you read this, resend the pull request over here:

• https://github.com/camelot-dev/camelot

[FelixSchwarz]

It would be really nice to get this functionality in camelot. @simonghrt Can you create a new PR for the camelot-dev repo?

[stevenkissack]

We'd also love this over using tempfile!