hint to single-file pyinstaller binaries from README

README.rst

@@ -63,6 +63,10 @@ Main features
     Backup archives are mountable as userspace filesystems for easy interactive
     backup examination and restores (e.g. by using a regular file manager).
 
+**Easy installation**
+    For Linux, Mac OS X and FreeBSD, we offer a single-file pyinstaller binary
+    that does not require installing anything - you can just run it.
+
 **Platforms Borg works on**
   * Linux
   * Mac OS X