Add runtime rtp getter (and in cli and configuration types)

src/cli.rs

@@ -33,5 +33,9 @@ impl<'a> CliConfig<'a> {
     pub fn is_debugging(&self) -> bool {
         self.cli_matches.is_present("debug")
     }
+
+    pub fn get_rtp(&self) -> Option<String> {
+        self.cli_matches.value_of("rtp").and_then(|s| Some(String::from(s)))
+    }
 }
 

src/configuration.rs

@@ -57,6 +57,10 @@ impl Configuration {
         format!("{}{}", self.rtp, self.store_sub)
     }
 
+    pub fn get_rtp(&self) -> String {
+        self.rtp.clone()
+    }
+
 }
 
 fn rtp_path(config: &CliConfig) -> String {

src/runtime.rs

@@ -72,4 +72,12 @@ impl<'a> Runtime<'a> {
         self.config.is_debugging() || self.configuration.is_verbose()
     }
 
+    pub fn get_rtp(&self) -> String {
+        if let Some(rtp) = self.config.get_rtp() {
+            rtp
+        } else {
+            self.configuration.get_rtp()
+        }
+    }
+
 }