don't pull attributes feature of tracing

Author: matklad

Cargo.toml

@@ -9,7 +9,7 @@ repository = "https://github.com/davidbarsky/tracing-tree"
 readme = "README.md"
 
 [dependencies]
-tracing = "0.1"
+tracing = { version = "0.1", default-features = false, features = ["std"] }
 tracing-subscriber = { version = "0.2", default-features = false, features = ["registry", "fmt"] }
 termcolor = "1.1"
 ansi_term = "0.12"
@@ -20,6 +20,7 @@ tracing-log = { version = "0.1", optional = true }
 default = ["tracing-log"]
 
 [dev-dependencies]
+tracing = { version = "0.1", default-features = false, features = ["std", "attributes"] }
 glob = "0.3"
 assert_cmd = "1"
 log = "0.4"