doc: document some minimal dependency versions

See GH issue #2 for more information:

 * #2

Suggested-by: Thordur Bjornsson <[email protected]>
Signed-off-by: Paul Moore <[email protected]>

Author: pcmoore

README

@@ -31,7 +31,9 @@ Documentation is also available at:
 
 * Installing the package
 
-Using go get:
+The libseccomp-golang bindings require at least Go v1.2.1 and GCC v4.8.4;
+earlier versions may yield unpredictable results.  If you meet these
+requirements you can install this package using the command below:
 
 	$ go get github.com/seccomp/libseccomp-golang