Add support for defining template variables of the following form:
{variables, [{appid, "mochiwebapp"},
{author, "Mochi Media <dev@mochimedia.com>"},
{year, "2010"},
{version, "0.1"},
{port, 8080},
{dest, "{{appid}}"}]}.
Where dest may be overridden on the commandline but will default to
being the appid. Mochiweb uses this so that we can create new
projects from the template in a configurable directory.
So
$ rebar create template=mochiwebapp dest=foo appid=bar
I thought about special casing dest but figured it might be generally
useful to be able to nest template vars.
However this patch only does one level of resolution. So if
{variables, [{foo, "{{bar}}"},
{bar, "{{foo}}"}]}.
then bar will end up being the literal string {{bar}} and foo the
literal string {{foo}}.
{file,In,Out,true} = render with mustache
{file,In,Out,false} = do not render with mustache (leave as-is)
old-form {file,In,Out} is equivalent to {file,In,Out,true}
