Modify the config parser to use symbolized key and group names

[tacticiankerala]

When I parsed a configuration file, the hash keys and group names where represented as string.
example:

{
  "foo" => "bar",
  "baz" => "quux",
  "123" => "456"
}

But, I think it will be much more convenient to deal with symbols in that case rather than strings.
example:

{
  :foo => "bar",
  :baz => "quux",
  :"123" => "456"
}

Also, I have modified the ability to add value and add group to support the above behavior.

I have added tests for add value and add group behavior and all the tests are passing.

[tacticiankerala]

The build is failing in Ruby 1.8, JRuby 1.8 and Ree. I will look into the issue.

[tacticiankerala]

It was failing because in the tests the method 'sort' was used to compare two arrays of groups. But unfortunately ruby 1.8 does not have sort operator implemented on symbols.

I have modified the tests not to use sort operator .

[derks]

I haven't had a chance to test this out yet... however, do your changes continue to support "string" keys? If not, it would completely break backward compatibility which would not be ideal. Appreciate your feedback either way!