Update documentation for Kaldi path configuration

[shuttle1987]

Currently there's a mismatch between how the settings.ini file is loading the Kaldi root path and how the documentation explains the same.

The documentation expects to read in the key for KALDI_ROOT but the current config.py file attempts to look at KALDI_ROOT_PATH. This issue was revealed by #237

See PR #238 for my fix for this issue.