fix client build instructions

README.rst

@@ -71,14 +71,21 @@ the ``libav`` suite (``avconv``).
 On a Debian-based system, ``apt-get install libav-tools portaudio19-dev``
 should do.
 
+* ensure that the GOPATH environment variable is set. For instance,
+  the following command will use a directory called ``go`` under
+  your $HOME:
+
+    $ export GOPATH=$HOME/go
+
 * install the ``godep`` tool:
 
-    $ cd $GOPATH/src/git.autistici.org/ale/djrandom
-    $ export PATH=$PATH:$GOPATH/bin
     $ go get github.com/tools/godep
+    $ export PATH=$PATH:$GOPATH/bin
 
 * install the client binaries::
 
+    $ cd $GOPATH/src/git.autistici.org/ale/djrandom
+    $ make
     $ godep install ./client/...
 
 You should now have ``djplay``, ``djupload`` and ``djmpd`` in ``$GOPATH/bin``.