README.md typo

extractmd/README.md

+11/11/2016 v1.0
+
+in extractmd.h
+ext4_super_group -> extractmd_super_group
+ext4_group_desc  -> extractmd_group_desc
+
+How to use?
+
+1. in your command line
+insert extractmd kernel module.(needs root permit)
+~#insmod extractmd.ko
+
+2. Then, you should make a test code.
+"test.c" is an example.
+
+/* Open */
+int fd = open("/dev/extractmd", O_RDWR);
+
+/* super_block in user space */
+struct extractmd_super_block super_block;
+
+/* ioctl will copy super_block from kernel space */
+inctl(fd, &super_block);
+
+/* Now super_block is copied
+ * ...do sometiing here with super_block...
+ */
+
+/* Close */
+close(fd);