Support parsing paths specified with pathlib

[AnjoMan]

pathlib was added to the standard librarly as of Python 3.4.
This adds support for calling Graph.parse on a file specified
using a pathlib object.

Proposed Changes

• if the source is specified as a Path object or subtype, call str on it
• pathlib objects implement str precisely for this purpose: https://docs.python.org/3/library/pathlib.html

[coveralls]

Coverage increased (+0.006%) to 75.673% when pulling 92e49ef on AnjoMan:support-parsing-pathlike-object into 56dc420 on RDFLib:master.

[AnjoMan]

please add the label hacktoberfest-accepted

[ashleysommer]

Hi @AnjoMan
This looks like a good change, especially now that python 2 (and python <=3.5) are no longer supported in future versions of RDFLib, and Pathlib is becoming more popular in the Python community.

We will discuss this more formally tomorrow at our RDFLib maintainers meeting.

I'm sorry, we are not participating in DigitalOcean's Hacktoberfest campaign.