Fix #229: make sure rebar searches for templates

Commit 83b6dd7 updated rebar to a version that is no longer recursive by
default when searching for templates for its "create" subcommand. Add the
"-r" option to the rebar invocation in scripts/new_webmachine.sh to make
sure it finds its templates properly.
Merge pull request #230 from vinoski/fix-new-wm-script

Fix #229: make sure rebar searches for templates

Reviewed-by: kellymclaughlin,kellymclaughlin