README: maven added to Fedora prerequisites

Build failed on my Fedora 20 due to lack of maven package.

Reviewed-by Zhi Yong Wu <zwu.kernel@gmail.com>
Signed-off-by: Dmitry Fleytman <dmitry@daynix.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

README.md

@@ -28,7 +28,7 @@ First, install prerequisite packages:
 **Fedora**
 
 ```
-yum install ant autoconf automake boost-static gcc-c++ genromfs libvirt libtool flex bison qemu-system-x86 qemu-img
+yum install ant autoconf automake boost-static gcc-c++ genromfs libvirt libtool flex bison qemu-system-x86 qemu-img maven
 ```
 
 **Debian**