let parsed = FieldStringParser.parse('username:(type:string, size:15, something:true),password:string,email:field({type: string, size: 40}),nickname:field(string),foo,bar');

let produces = { username:
   { argumentString: '{ type: \'string\', size: 15, something: true }',
     definition: { type: 'string', size: 15, something: true } },
  password:
   { argumentString: '{ type: \'string\' }',
     definition: { type: 'string' } },
  email:
   { argumentString: '{ type: \'string\', size: 40 }',
     definition: { type: 'string', size: 40 } },
  nickname:
   { argumentString: '{ type: \'string\' }',
     definition: { type: 'string' } },
  foo:
   { argumentString: '{ type: \'string\' }',
     definition: { type: 'string' } },
  bar:
   { argumentString: '{ type: \'string\' }',
     definition: { type: 'string' } } }