Fix handling of raw rebar deps
Deprecate is_regex/1 and is_range/1

Conflicts:
	lib/elixir/lib/string.ex
Start app after changing System.argv on 'mix run'
Fix `String.slice error`

    iex(76)> String.slice("string", 0..-2)
    nil # you see here is the issue, it shouldn't return `nil`
    iex(77)> String.slice("string", 1..-2)
    "trin"
    iex(78)> String.slice("string", -5..-2)
    "trin"
Add test case for  bug