Merged pull request #119 from jbernard/develop.

Set GITFLOW_DIR correctly if git-flow is a symbolic link
diff --git a/git-flow b/git-flow
index fa87e71..f30db32 100755
--- a/git-flow
+++ b/git-flow
@@ -42,7 +42,7 @@
 	set -x
 fi
 
-export GITFLOW_DIR=$(dirname "$0")
+export GITFLOW_DIR=$(dirname $(readlink "$0"))
 
 usage() {
 	echo "usage: git flow <subcommand>"