readline added to install docs

Rev: src/README:1.5

src/README

@@ -5,9 +5,9 @@ This is what you need to do to install uLPC:
    if you want to install ulpc in /foo/bar, default is /usr/local.
 
    You might have to set the environment variables C_INCLUDE_PATH and
-   LD_LIBRARY_PATH to enable the configure script to find gdbm and gmp.
-   If the configure script does not find those libraries those modules
-   will not be available.
+   LD_LIBRARY_PATH to enable the configure script to find gdbm, readline
+   and gmp. If the configure script does not find those libraries those
+   modules will not be available.
 
 2) edit config.h and Makefile to suit your purposes.
    I've tried to make it so that you don't have to change config.h or