Fix pathing of config file so you can run from anywhere

[rdelpret]

trails -o
Traceback (most recent call last):
  File "/Users/rdelprete/github/ski-trails/trails", line 67, in <module>
    main()
  File "/Users/rdelprete/github/ski-trails/trails", line 64, in main
    cli()
  File "/Users/rdelprete/github/ski-trails/trails", line 27, in cli
    config = get_config()
  File "/Users/rdelprete/github/ski-trails/trails", line 15, in get_config
    with open("config.yaml", "r") as f:
FileNotFoundError: [Errno 2] No such file or directory: 'config.yaml'