Add support for "query" variable

[dinoboff]

• [x] support query during parsing.

• [x] support query during evaluation.

• [x] add API to provide query to read operations (and update other operation signature).

  Database.prototype.read(path: string, options: {now?: number, query?: object}): Result
  Database.prototype.write(path: string, value: any, options: {now?: number, priority?: any}): Result
  Database.prototype.update(path: string, patch: object, options: {now?: number}): Result

  It's backward compatible with the 3.0.x signature.

• [x] add query to chai matcher:

  chai.Assertion.readWith(options: {query?: object, now?: number})

  e.g.:

  expect({uid}).can.readWith({query: {
    orderByChild: 'owner',
    equalTo: uid
  }}).path('/');

• [x] add query to jasmine matcher.

  expect(auth).canRead(path: string, options: {now?: number, query?: object})
  expect(auth).cannotRead(path: string, options: {now?: number, query?: object})

  e.g.:

  expect({uid}).canRead('/', {query: {
    orderByChild: 'owner',
    equalTo: uid
  }});

Fix #142

[coveralls]

Coverage increased (+0.4%) to 94.92% when pulling edc2a0d4df9599593c43459c21270685c5de6f5d on dinoboff:feat/query into 09f2670fdfb03d926001ab1e491921a850d0f7cb on goldibex:master.