Added requirements.txt file, other bits

• Based on http://stackoverflow.com/questions/11301650/how-to-escape-indicator-characters-i-e-or-in-yaml#answer-22483116, added a `|` [here](https://github.com/jheasly/secret-santa/blob/master/config.yml.template#L29 ), which will allow for indicator characters in `Message` portion of YAML config file.
• Fixed spelling of `receiver(s)`.