Remove CONTRIBUTORS file to prefer dynamically generate it

Per discussion in the dev@ list, maintaining the CONTRIBUTORS file manually is hard to do.

Most ASF projects defer this to team page or retrieveing it from JIRA or git commit list
for every release if needed.

This PR proposes to remove it and defer to dynamically created per release.

Author: Henry Saputra <henry.saputra@gmail.com>

Closes #123 from hsaputra/remove_contributors_file and squashes the following commits:

e235cbc [Henry Saputra] Per discussion in the dev@ list maintaining the CONTRIBUTORS file manually is hard. Most ASF projects defer this to team page or retrieveing it from JIRA or git commit list for every release.