Update praw to 3.6.2; make package installable on F28 and up.
This commit updates praw to 3.6.2, the most recent release in the
3.6.x series. There are newer praw releases, but they split the software
into two packages (prawcore and praW), which will require an additional
review. praw was not installable on Fedora 28 and above due to
overly strict dependency verison guards. This commit fixes this and also
updates to 3.6.2.
A future commit will update to the latest praw release.