Support parsing rebar.config files

[Wilfred]

These are Erlang syntax (e.g. GitHub highlights them as Erlang), but I get ERROR nodes when I try to parse them. For example, the following file:

{erl_opts, [
    {parse_transform, lager_transform},
    debug_info
]}.
{deps, [
    {poolboy, "1.5.2"},
    bcrypt,
    {mcd, {git, "https://github.com/EchoTeam/mcd.git", {ref, "b5b4a32"}}}
]}.

Produces the following parse tree:

source_file (0, 0) - (9, 0)
  ERROR (0, 0) - (8, 3)
    { (0, 0) - (0, 1) "{"
    atom (0, 1) - (0, 9) "erl_opts"
    , (0, 9) - (0, 10) ","
    [ (0, 11) - (0, 12) "["
    { (1, 4) - (1, 5) "{"
    atom (1, 5) - (1, 20) "parse_transform"
    , (1, 20) - (1, 21) ","
    atom (1, 22) - (1, 37) "lager_transform"
    } (1, 37) - (1, 38) "}"
    , (1, 38) - (1, 39) ","
    atom (2, 4) - (2, 14) "debug_info"
    ] (3, 0) - (3, 1) "]"
    } (3, 1) - (3, 2) "}"
    . (3, 2) - (3, 3) "."
    { (4, 0) - (4, 1) "{"
    atom (4, 1) - (4, 5) "deps"
    , (4, 5) - (4, 6) ","
    [ (4, 7) - (4, 8) "["
    { (5, 4) - (5, 5) "{"
    atom (5, 5) - (5, 12) "poolboy"
    , (5, 12) - (5, 13) ","
    string (5, 14) - (5, 21) "\"1.5.2\""
    } (5, 21) - (5, 22) "}"
    , (5, 22) - (5, 23) ","
    atom (6, 4) - (6, 10) "bcrypt"
    , (6, 10) - (6, 11) ","
    { (7, 4) - (7, 5) "{"
    atom (7, 5) - (7, 8) "mcd"
    , (7, 8) - (7, 9) ","
    { (7, 10) - (7, 11) "{"
    atom (7, 11) - (7, 14) "git"
    , (7, 14) - (7, 15) ","
    string (7, 16) - (7, 53) "\"https://github.com/EchoTeam/mcd.git\""
    , (7, 53) - (7, 54) ","
    { (7, 55) - (7, 56) "{"
    atom (7, 56) - (7, 59) "ref"
    , (7, 59) - (7, 60) ","
    string (7, 61) - (7, 70) "\"b5b4a32\""
    } (7, 70) - (7, 71) "}"
    } (7, 71) - (7, 72) "}"
    } (7, 72) - (7, 73) "}"
    ] (8, 0) - (8, 1) "]"
    } (8, 1) - (8, 2) "}"
    . (8, 2) - (8, 3) "."

[alanz]

Thanks for the report. I intend getting to this soon.