Fix 658 and compiler complaints (#661)

* Tried but failed to fix `cargo build` complaint about unused #[macro use]. See also 7a803a8dc1
* Compiler complaints be-gone
* Give sumtree tests method-tagged folder names so they don't overwrite each others' files
Fixes #658

src/bin/grin.rs

@@ -499,7 +499,7 @@ fn wallet_command(wallet_args: &ArgMatches, global_config: GlobalConfig) {
 				minimum_confirmations,
 				dest.to_string(),
 				max_outputs,
-				(selection_strategy == "all"),
+				selection_strategy == "all",
 			);
 			match result {
 				Ok(_) => info!(