Python 3 and formatting spaces

[kinow]

On Ubuntu LTS, I get the following error due to a mixture of tabs, spaces, and probably local settings:

python setup.py install
running install
running build
running build_py
copying practnlptools/tools.py -> build/lib/practnlptools
running install_lib
copying build/lib/practnlptools/tools.py -> /home/kinow/Development/python/anaconda3/lib/python3.5/site-packages/practnlptools
byte-compiling /home/kinow/Development/python/anaconda3/lib/python3.5/site-packages/practnlptools/tools.py to tools.cpython-35.pyc
Sorry: IndentationError: expected an indented block (tools.py, line 53)

Normally I don't have problems with tabs / spaces in other libraries, and I can see the indentation online via GitHub. So I believe it could be an issue with encoding, different settings in git, etc. This PR normalizes the code to use just spaces, which should make it a bit easier for devs in different platforms to edit / use it.