use Copy instead of unsafe

src/run.rs

@@ -79,22 +79,16 @@ impl Run{
 		}
 	}
 	pub fn finish(&mut self,time:Time)->Result<(),Error>{
-		//code based on std::mem::replace
-		let dest=&mut self.state;
-		//let's ignore ownership rules for a moment
-		unsafe{
-			let state=std::ptr::read(dest);
-			match state{
-				RunState::Created=>Err(Error::NotStarted),
-				RunState::Started{timer}=>{
-					let src=RunState::Finished{
-						timer:timer.pause(time),
-					};
-					std::ptr::write(dest,src);
-					Ok(())
-				},
-				RunState::Finished{..}=>Err(Error::AlreadyFinished),
-			}
+		//this uses Copy
+		match &self.state{
+			RunState::Created=>Err(Error::NotStarted),
+			RunState::Started{timer}=>{
+				self.state=RunState::Finished{
+					timer:timer.pause(time),
+				};
+				Ok(())
+			},
+			RunState::Finished{..}=>Err(Error::AlreadyFinished),
 		}
 	}
 	pub fn flag(&mut self,flag_reason:FlagReason){