A simple macro to determine if an environment is
a "development" environment.
Built because some of us (me) are lazy and don't feel like
copy-pasting the same check for development environments over and over
again.
:heart:
Ex:
```
#[macro_use] extern crate is_dev;
fn test_is_dev() {
let e: bool = is_dev!("ENV", "development");
assert!(e);
}
```