put -lcurl at the end for the sake of linux systems
Move towards ENV based configuration.

In order to make it easier to run container via process supervisors, on
Heroku, or in containers, we are moving to an ENV based configuration
style.

The following env vars are required:

* URL - the url to be monitored
* NAME - the name of this check, can be used downstream
* LOCATION - the location of this sensor, can be used downstream
Merge pull request #2 from gorsuch/env

Config via ENV