make sure custom rvmrc works too if you directly cd into a subdir [ci skip]

.rvmrc

 #!/bin/bash
-if [ -e '.rvmrc_custom' ]; then
-  source .rvmrc_custom;
+
+root=$(dirname $(readlink -e $BASH_SOURCE))
+if [ -e "${root}/.rvmrc_custom" ]; then
+  source ${root}/.rvmrc_custom
 else
   rvm --create use ree-1.8.7-2011.03@diaspora
 fi