move to using absolute imports (for python3)

[AlJohri]

• move benchmark.py outside of the paradox folder (it would require running as python -m paradox.benchmark if you wanted to keep it in the folder)
• use computed relative paths GLOVE_FOLDER and CORPUS_FOLDER starting from the root paradox folder (for being able to import paradox in another project where paths relative to CWD don't work)

ref on need for abs imports: https://chrisyeh96.github.io/2017/08/08/definitive-guide-python-imports.html#absolute-vs-relative-import