Add more comments and examples.

tests/arrays.rs

@@ -35,7 +35,7 @@ fn test_array_with_structs() -> Result<(), EvalAltResult> {
             self.x = new_x;
         }
 
-        fn new() -> TestStruct {
+        fn new() -> Self {
             TestStruct { x: 1 }
         }
     }

tests/float.rs

@@ -38,7 +38,7 @@ fn struct_with_float() -> Result<(), EvalAltResult> {
             self.x = new_x;
         }
 
-        fn new() -> TestStruct {
+        fn new() -> Self {
             TestStruct { x: 1.0 }
         }
     }

tests/get_set.rs

@@ -16,7 +16,7 @@ fn test_get_set() -> Result<(), EvalAltResult> {
             self.x = new_x;
         }
 
-        fn new() -> TestStruct {
+        fn new() -> Self {
             TestStruct { x: 1 }
         }
     }

tests/method_call.rs

@@ -12,7 +12,7 @@ fn test_method_call() -> Result<(), EvalAltResult> {
             self.x += 1000;
         }
 
-        fn new() -> TestStruct {
+        fn new() -> Self {
             TestStruct { x: 1 }
         }
     }

tests/mismatched_op.rs

@@ -19,7 +19,7 @@ fn test_mismatched_op_custom_type() {
     }
 
     impl TestStruct {
-        fn new() -> TestStruct {
+        fn new() -> Self {
             TestStruct { x: 1 }
         }
     }