Basic Github user stats extractor

Retrieve and count unique users who contributed to a repository

Parameters:

1. List of repositories (space-separated string),

2. Github token to use (string),

3. How far in time should data be fetched (date).

Example query:

$ bash stats.sh \
    "repo1 repo2 repo3"
    "my_very_secret_token"\
    "2018-01-01"