Add cookies 49

Partial implementation of Issue #49.

Here's what's included:

- `--cookie="bar=foo"` command line argument handling.
- `cookies=[]` array handling in config.json

What's not included:
- `--cookies-file` syntax handling. Was unsure of how to proceed, since I couldn't find any exposed functions in phantomjs that would let you load the cookie jar binary, and parsing a cookie jar "binary" in JS didn't seem particularly useful.

Cookies-file handling might need to split out into another bug, or I may need some help!