Less ambiguous README.md, mention build reqs

README.md

-To build Gluon, use the following commands after checking out the repository:
+To build Gluon, after checkeing out the repository change to the source root directory
+to  perform the following commands:
 
     git submodule update --init                                  # Get other repositories used by Gluon
     git clone git://github.com/freifunk-gluon/site-ffhl.git site # Get the Freifunk Lübeck site repository - or use your own!
@@ -9,7 +10,11 @@ the images only, just use:
 
     make images
 
-The built images can be found in the directory /images.
+The built images can be found in the directory ./images.
+
+For the build reserve 6GB of disk space. The building requires packages
+for subversion, ncurses headers (libncurses-dev) and zlib headers
+(libz-dev).`
 
 
 There are three levels of 'make clean':