Prevent overlooking a compilation warning by removing the target beam
file after fail_on_warning failure.

abnfc is an ABNF parser generator.
Options are:
	- doc_root (defaults to "src")
	- out_dir (defaults to "src")
	- source_ext (defaults to ".abnf")
	- module_ext (defaults to "")

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}}.

Conflicts:
	priv/templates/simplenode.runner

mustache:render("{{banan}}", dict:from_list([{banan, true}])).

** exception error: no function clause matching mustache:escape(true,[])
     in function  erl_eval:do_apply/5
     in call from erl_eval:expr/5
     in call from erl_eval:expr/5
     in call from mustache:render/3

- Check the existence of first_files and fail if they are not present
 - Get first_files lists from local instead of inherited config
   definitions, since they only make sense in the local context

Using rebar's commandline, enable/disable 'debug_info' for
compilation. This feature if added to all rebar compilers could help
simplify and standardize this common use case for all rebar build
targets.

e.g. {dialyzer_opts, [{plt, "~/.dialyzer_plt.R14B"}]}.

Use rebar_utils:find_executable/1 that wraps the
path in quotes to make it work even if it contains
whitespace.

Change git downloads and updates to not create branches and fix git
tag handling.

If rebar tries to clean the .app file (because there's a .app.src file)
and it doesn't exist (possibly because of a bad compile), don't fail.

Make the error message newline terminated and, if possible, log the name
of the module in which the failure occured.