Update the README with the needed python dependencies (wikipedia, duckduck)

[m040601]

Was trying to test run this, but was complaining about missing python modules. They are not listed on the readme as requirements..

Ended up figuring out that for wikipedia it needs,
https://github.com/goldsmith/Wikipedia. That is provided by the package python-wikipedia in Archlinux.

For duckduck go, could not find out which python module is this needed "ddg" one,

  File "/home/a1/.elinks/soupmonkey/__init__.py", line 9, in <module>
    modules.append(__import__(module[:-3], locals(), globals()))
ModuleNotFoundError: No module named 'ddg'

[RobSis]

Hey. You don't actually need any libraries to run this except BeautifulSoup4. The module 'ddg' is actually the ddg.py file in the repostiory.

I guess the reason of those error messages is wrong location of scripts, or something like that. Did you put all files from this repo into your ~/.elinks directory?