Update RVM shell commands

When finding a Ruby command these are now tried in order:
1. rbenv
2. rvm
3. rvm legacy
4. system ruby

Fixes #23

Author: Mike Foley

templates/hooks/commit-msg

@@ -26,11 +26,15 @@ if [ -z "$GIT_BRANCH_NAME" ]; then
   exit 0
 fi
 
-if which rvm > /dev/null 2>&1
-then cmd="rvm default do ruby"
-elif which rbenv > /dev/null 2>&1
-then cmd="rbenv exec ruby"
-else cmd="ruby"
+# find appropriate Ruby command
+if which rbenv > /dev/null 2>&1; then
+  cmd="rbenv exec ruby"
+elif which ruby-rvm-env > /dev/null 2>&1; then
+  cmd="ruby-rvm-env"
+elif which rvm > /dev/null 2>&1; then
+  cmd="rvm default do ruby"
+else
+  cmd="ruby"
 fi
 
 # allow user input if running in a terminal