No sys.path mangling.

Not sure if this was ever necessary, but now it is causing failures on
readthedocs; rtd installs the project from a wheel, so it gets installed
to site-packages. When the pynng directory gets added to sys.path, it
gets picked up before the version in site packages. This is a problem
because rtd does not build the package "in place", so there are no
shared libraries where they are expected.

At least I *hope* that is what is going on.

docs/conf.py

@@ -12,10 +12,6 @@
 # add these directories to sys.path here. If the directory is relative to the
 # documentation root, use os.path.abspath to make it absolute, like shown here.
 #
-import os
-import sys
-
-sys.path.insert(0, os.path.abspath(".."))
 
 
 # -- Project information -----------------------------------------------------