fixing memleak of input char*

- adding missing free() calls
- dont malloc ourselves as getline() also does a malloc
  (and anyway called realloc before if the size_t was
   smaller then the actual len(input-line) to behaviour
   is the same!)

challenge/challenge.c

@@ -3,23 +3,26 @@
 
 int main() {
     int bytes_read;
-    size_t nbytes = 10; 
-    char **my_string = malloc(sizeof(char**));
+    size_t nbytes = 0;
+    char *my_string = NULL;
     char *password = "23door42\n";
 
     puts("Please enter Password: ");
 
-    bytes_read = getline(my_string, &nbytes, stdin);
+    bytes_read = getline(&my_string, &nbytes, stdin);
 
     if(bytes_read == -1) {
         puts("Error");
+        free(my_string);
         return -1;
     } else {
-        if (strcmp(*my_string, password) == 0) {
+        if (strcmp(my_string, password) == 0) {
             puts("Success");
+            free(my_string);
             return 0;
         } else {
             puts("How about no?!");
+            free(my_string);
             return -1;
         }
     }