Drop a reference to the tracing crate

This is otherwise not referenced. Remove the need to add a dependency on
`tracing` from the README.

CHANGELOG.md

@@ -4,6 +4,7 @@ Unreleased
   `test_case` crate), that may not have been parsable in the past
 - Removed generated `test_impl` function, which could have "leaked" into
   test cases (#28)
+- Eliminated dependency on `tracing` crate
 
 
 0.2.12

README.md

@@ -120,7 +120,6 @@ enabling the `log` or `trace` feature, respectively). E.g.,
 ```toml
 [dev-dependencies]
 env_logger = "*"
-tracing = {version = "0.1", default-features = false}
 tracing-subscriber = {version = "0.3", default-features = false, features = ["env-filter", "fmt"]}
 ```
 

src/lib.rs

@@ -164,12 +164,11 @@ fn expand_tracing_init() -> Tokens {
         }
       };
 
-      let subscriber = ::tracing_subscriber::FmtSubscriber::builder()
+      let _ = ::tracing_subscriber::FmtSubscriber::builder()
         .with_env_filter(::tracing_subscriber::EnvFilter::from_default_env())
         .with_span_events(__internal_event_filter)
         .with_test_writer()
-        .finish();
-      let _ = ::tracing::subscriber::set_global_default(subscriber);
+        .try_init();
     }
   }
   #[cfg(not(feature = "trace"))]