Modify run_discordbot.js to take command line args

[kyrivanderpoel]

The user should be able to pass run_discordbot.js a command line argument for a filename. This filename will be used in place of the hardcoded configuration file that currently resides in the code.

node examples/run_discordbot.js -f plugin_configuration.json
node examples/run_discordbot.js -f /home/me/path/to/my/configuration.json

This allows one to update the start command in package.json to use the -f argument and specify the configuration file, so that the prod bundle may target the default configuration file in the bin directory instead of the examples directory.