Implement `parse` method to parse data in files

[qfox]

Ref: #6

Methods:

• [ ] parse(data: {version: ?string, blocks: ?object[], decl: ?object[]): BEMEntityParts[]

The method should determine the format of the file content.

BEMDECL 1.0

exports.blocks = [
    { name: 'block' }
];

or

exports.version = '1.0';
exports.decl = [
    { name: 'block' }
];

BEMDECL 2.0

exports.version = '2.0';
exports.decl = [
    { block: 'block' }
];

BEMDECL next

exports.version = 'next';
exports.decl = [
    { block: 'block' }
];

The method should translate any format to normalized BEMDECL 2.0.

var parse = require('bem-decl').parse;

// bemdecl-1.0.js
// exports.blocks = [
//     { name: 'block' }
// ];

parse(fs.readFileSync('bemdecl-1.0.js')); // [{ block: 'block' }]

[qfox]

Prbbly parse isn't the best name for this method. Any other suggestions?