Consider eliminating use of requests for remote workflow functionality

[applio]

With the merging of PR #12, there is now a dependency on the requests module for remote workflow functionality. While the use of this popular module is very appropriate, it does deviate from the goal of having knime.py not depend upon anything outside of Python itself. Even the pandas module is purely optional but when it comes to remote workflow functionality the same can not be said for requests.

Either this functionality should be supplied by the Python Standard Library's urllib.request and related modules or the stated goal of depending upon nothing more than a standard Python installation should be updated.

[greglandrum]

my two cents: I'm not sure what it would look like in this particular case, but in my experience code written with requests tends to be considerably simpler and easier to read than the alternatives using the standard library. Given that requests is actively maintained and widely used, I think it makes sense to continue to use it.