Fix unmarshaling of literal keys

Ref #427.

parser.go

@@ -594,7 +594,7 @@ func (p *parser) parseSimpleKey(b []byte) (key, rest []byte, err error) {
 	}
 
 	if b[0] == '\'' {
-		key, rest, err = scanLiteralString(b)
+		key, rest, err = p.parseLiteralString(b)
 	} else if b[0] == '"' {
 		key, rest, err = p.parseBasicString(b)
 	} else if isUnquotedKeyChar(b[0]) {

unmarshaler_test.go

@@ -210,6 +210,21 @@ func TestUnmarshal(t *testing.T) {
 				}
 			},
 		},
+		{
+			desc: "issue 427 - quotation marks in key",
+			input: `'"a"' = 1
+					"\"b\"" = 2`,
+			gen: func() test {
+				m := map[string]interface{}{}
+				return test{
+					target:   &m,
+					expected: &map[string]interface{}{
+						`"a"`: int64(1),
+						`"b"`: int64(2),
+					},
+				}
+			},
+		},
 		{
 			desc:  "multiline basic string",
 			input: `A = """\