Implement 'rebar help CMD1 CMD2' and extend common 'rebar help' msg

* allow plugins to print help message for implemented commands
* append core rebar.config options to common 'rebar help' message
Change simplenode template files to work on more platforms

When developing Riak, we have found bugs and other issues due
to the number of platforms we support.

Here is an overview of the changes:
  -  Fix command-line syntax for commands to work on *BSD / Sun
  -  Add chkconfig and getpid to nodetool
  -  Replace platform specific 'kill' commands with a nodetool
	getpid method
  -  Fix RUNNER_USER settings to work on *BSD
Support reading mustache 'lists' from files

This commit add support for reading mustache 'lists' from files, so you
can use the list section functionality when templating things.

An example of the list syntax is as follows:

{package_commands, {list, [[{name, "riak"}], [{name, "riak-admin"}], [{name, "search-cmd"}]]}}.

Then you can, for each of the list elements, render some text:

{{#package_commands}}
chmod +x bin/{{name}}
{{/package_commands}}
Fix handling of Unicode characters in env vars
Merge pull request #22 from tuncer/help

Implement 'rebar help CMD1 CMD2' and extend common 'rebar help' msg
Merge pull request #59 from Vagabond/adt-read-lists-from-files

Support reading mustache 'lists' from files
rebar_core: document pre-dirs association
rebar_core: remove useless return after ?ABORT call
rebar_core: fix broken indentation
Update rebar repo urls
Merge pull request #55 from jaredmorrow/jem-simplenode-multi-platform

Change simplenode template files to work on more platforms
Remove unnecessary bar
Merge pull request #69 from tuncer/repo-url

Update rebar repo urls
Merge pull request #38 from tuncer/fix-sub_dir-association

rebar_core: fix sub dir association
Remove hg from integration tests; git is defacto standard at this point
Fix missing call to cwd_predirs
Merge pull request #68 from nevar/fix_unicode_promt

Fix unicode
Add travis target to make it easier to reproduce failures locally
Makefile: call Dialyzer with -nn flag

This speeds up 'make dialyzer' for the common case of Erlang/OTP built
without --enable-native-libs.
simplenode.reltool.config: use default sys-level mod_cond setting

As discussed here
http://erlang.org/pipermail/erlang-questions/2012-December/071135.html
change the reltool spec to use the default sys-level mod_cond setting.