Add colors to output

[eboody]

Added some colors behind a feature flag color-output to make it easier for some people to scroll through long lists of request/response outputs.

Methods are colored: (GET, POST, PUSH, DELETE) = (Blue, Green, Yellow, Red)
Status codes (200-299, 300-399, 400-499, 500-599) = (Green, Blue, Yellow, Red)

If the response body is just text, the output will be the same color as the status code.
JSON response bodies will be colored based off the colored_json crate.

For brevity, the schema and host were stripped out of the URL (Please let me know if this is a bad idea!)

colored adds 21.6 kB
colored_json adds 13.6 kB
url adds 75.7 kB

considering im only using the url crate to extract the path it might be worth it to just do some string manipulation instead since its the biggest crate of the three by far even though the crates are behind the feature flag.

[jeremychone]

Thanks, this is an awesome addition. I will look at it and merge it next week.