[WIP] PDFHandler accepts file like objects

[pqrth]

Closes #91

[vinayak-mehta]

Closing in favor of #236.

[pilotjoe]

Closing in favor of #236.

@vinayak-mehta If I understand correctly, #236 only resolves reading from a URL but not reading a file like object. I have run across situations where it would be very useful to read from a file like object. For example, reading PDFs from SharePoint where authentication from requests is needed, an HTTP 401 Unauthorized error would be produced just passing the URL to read_pdf(). It appears the only way to currently handle these cases is to pull the PDF using another library such as requests, save the file locally, pull the file back in using read_pdf(), then deal with the housekeeping of written files (or use something like tempfile as mentioned in #158). This is less efficient than having read_pdf() read directly from a file like object.

[pilotjoe]

For anyone running across this, it appears #376 will be addressing this. It is also discussed in camelot-dev/camelot#103