Add version-switch script

diff --git a/contrib/version-switch b/contrib/version-switch
new file mode 100755 (executable)
index 0000000..4b143c9
--- /dev/null
+++ b/contrib/version-switch
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+current=$(git tag | tail -n 1 | tail -c +2)
+grep -rl --exclude-dir=.git ${current} | \
+  while read line; do
+    sed -i "s/${current}/${1}/g" ${line}
+  done