Automatically download and extract libstemmer_c.tgz if libstemmer_c
directory doesn't exist
Add checking of MD5 checksum for downloaded libstemmer_c.tgz tarball
.travis.yml: Use `setup.py bootstrap` instead of downloading with curl
tarballfetcher.py: Make it work with Python 3
Merge pull request #8 from msabramo/automatically-download-libstemmer

Automatically download and extract libstemmer_c.tgz if libstemmer_c directory doesn't exist