Feature/scalar raw value

[menduz]

Added allowAnyEscape option to parser.

name: "Agustin \{test}"

Is now parsed as Scalar "Agustin \\{test}"

Added rawValue to Scalar, lets use this yaml fragment:

test: "hola\nmanola\{"

Before, and now without the new flag, we expect this result:

let yaml = `
test: "hola${'\\'}nmanola${'\\'}{"
`;

let result = yaml.load(yaml); 

result == { errors:
   [ YAMLException {
       name: 'YAMLException',
       reason: 'unknown escape sequence',
       mark:
        Mark {
          name: null,
          buffer: '\ntest: "hola\\nmanola\\{"\n\u0000',
          position: 21,
          line: 0,
          column: 20 },
       message: 'JS-YAML: unknown escape sequence at line 1, column 21' } ],
   ...
}

Now it works with the new allowAnyEscape flag

let options = { allowAnyEscape: true };
let yaml = `
test: "hola${'\\'}nmanola${'\\'}{"
`;

let result = yaml.load(yaml, options);

result == { errors: [],
  startPosition: 1,
  endPosition: 24,
  mappings:
   [ { key:
        { errors: [],
          startPosition: 1,
          endPosition: 5,
          value: 'test',
          kind: 0,
          parent: [Circular],
          doubleQuoted: false,
          rawValue: 'test',
          plainScalar: true },
       value:
        { errors: [],
          startPosition: 7,
          endPosition: 23,
          value: 'hola\nmanola\\{',
          kind: 0,
          parent: [Circular],
          doubleQuoted: true,
          rawValue: '"hola\\nmanola\\{"' }, // <-----
       startPosition: 1,
       endPosition: 23,
       kind: 1,
       parent: [Circular],
       errors: [] } ],
  kind: 2,
  parent: null }

[menduz]

It also solves #5

[KonstantinSviridov]

Hi, @menduz!

Thanks for the contribution.

[menduz]

@KonstantinSviridov thank you. Please also check PR #4