Added --stdin-data argument

This argument accepts a path to a file. The data contained in the file will be passed to the command via stdin.

Closes sharkdp/hyperfine#541

tests/example_stdin_data

@@ -0,0 +1 @@
+This data is passed to the command via stdin

tests/integration_tests.rs

@@ -215,6 +215,34 @@ fn runs_commands_using_user_defined_shell() {
         );
 }
 
+#[test]
+fn can_pass_file_data_to_command_via_stdin(){
+    hyperfine()
+        .arg("--runs=1")
+        .arg("--stdin-data=example_stdin_data")
+        .arg("--show-output")
+        .arg("cat")
+        .assert()
+        .success()
+        .stdout(
+            predicate::str::contains("This data is passed to the command via stdin")
+        );
+}
+
+#[test]
+fn fails_if_invalid_stdin_data_file_provided(){
+    hyperfine()
+        .arg("--runs=1")
+        .arg("--stdin-data=example_stdin_data_invalid")
+        .arg("--show-output")
+        .arg("cat")
+        .assert()
+        .failure()
+        .stderr(
+            predicate::str::contains("File containing stdin data 'example_stdin_data_invalid' does not exist")
+        );
+}
+
 #[test]
 fn returns_mean_time_in_correct_unit() {
     hyperfine_debug()