add method to get vec from config

src/helpers/config.rs

@@ -1,11 +1,18 @@
+use toml;
 use toml::value::Table;
 
 pub trait Config {
     fn get_string (&self, key: &str) -> Option<&str>;
+    fn get_vec (&self, key: &str) -> Option<Vec<toml::Value>>;
 }
 
 impl Config for Table {
     fn get_string (&self, key: &str) -> Option<&str> {
         self.get(key).and_then(|value| value.as_str())
     }
+
+    fn get_vec (&self, key: &str) -> Option<Vec<toml::Value>> {
+        self.get(key).and_then(|value| value.as_array())
+                     .map(|value| value.to_vec())
+    }
 }