Fix syntax detection for files called 'rails'

closes #1008

src/assets.rs

@@ -481,4 +481,15 @@ mod tests {
             "Bourne Again Shell (bash)"
         );
     }
+
+    #[test]
+    fn issue_1008() {
+        let test = SyntaxDetectionTest::new();
+
+        assert_eq!(
+            test.syntax_for_file_with_content("bin/rails", "#!/usr/bin/env ruby"),
+            "Ruby"
+        );
+        assert_eq!(test.syntax_for_file("example.rails"), "HTML (Rails)");
+    }
 }

src/syntax_mapping.rs

@@ -42,6 +42,11 @@ impl<'a> SyntaxMapping<'a> {
             )
             .unwrap();
 
+        // See #1008
+        mapping
+            .insert("rails", MappingTarget::MapToUnknown)
+            .unwrap();
+
         mapping
     }