display the percentage through the file that the cursor is at

A modeline may look like, for instance:

	NORMAL  [17%] src/presenters/mod.rs

as opposed to the previous:

	NORMAL  src/presenters/mod.rs

This is a small & slightly opinionated change.

src/presenters/mod.rs

@@ -11,16 +11,26 @@ fn path_as_title(path: &Path) -> String {
 }
 
 fn current_buffer_status_line_data(workspace: &mut Workspace) -> StatusLineData {
-    let modified = workspace.current_buffer().map(|b| b.modified()).unwrap_or(false);
+    let buffer = workspace.current_buffer();
+    let modified = buffer.as_ref().map(|b| b.modified()).unwrap_or(false);
+
+    let line_perc = buffer.map(|b| {
+        let line_total = b.line_count();
+        let line_at = b.cursor.position.line + 1;
+        let line_perc = (line_at * 100) / line_total;
+        format!("[{:2}%]", line_perc)
+    }).unwrap_or(String::new());
 
     let (content, style) = workspace.current_buffer_path().map(|path| {
         let mut title = path_as_title(path);
+        let mut style = Style::Default;
+
         if modified {
             title.push('*');
-            (title, Style::Bold)
-        } else {
-            (title, Style::Default)
+            style = Style::Bold;
         }
+
+        (format!(" {}{}", line_perc, title), style)
     }).unwrap_or((String::new(), Style::Default));
 
     StatusLineData {