README: Quick fix to document how to rebuild the configure script

Change-Id: I8712b7a865afe2072fb7dbcbc34804587f6aad42
diff --git a/README b/README
index a7b6093..8e85a71 100644
--- a/README
+++ b/README
@@ -5,7 +5,7 @@
 C99. The following components are available:
 
 * dtls
-  Basic support for DTLS with pre-shared key mode.
+  Basic support for DTLS with pre-shared key mode and RPK mode with ECC.
 
 * tests
   The subdirectory tests contains test programs that show how each
@@ -14,13 +14,17 @@
 BUILDING
 
 When using the code from the git repository at sourceforge, invoke
-'autoreconf' to re-create the configure script. To build for Contiki,
-place tinydtls into Contiki's apps directory and call 
-  ./configure --with-contiki.
 
-After configuration, invoke make to build the library and associated
-test programs. To add tinydtls as Contiki application, drop it into
-the apps directory and add the following line to your Makefile:
+  $ autoconf
+  $ autoheader
+  $ ./configure
+
+to re-create the configure script.
+
+On Contiki, place the tinydtls library into the apps folder. After
+configuration, invoke make to build the library and associated test
+programs. To add tinydtls as Contiki application, drop it into the
+apps directory and add the following line to your Makefile:
 
   APPS += tinydtls/aes tinydtls/sha2 tinydtls/ecc tinydtls