add a startAt option for angleAddr
add a startAt option for angleAddr

example:
> var ea = require('./lib/email-addresses');
undefined
> ea({input: '<foo@example.com>', startAt: 'angle-addr'})
{ ast:
   { name: 'angle-addr',
     tokens: '<foo@example.com>',
     semantic: '<foo@example.com>',
     children: [ [Object] ] },
  addresses: [] }
> ea({input: 'foo@example.com', startAt: 'angle-addr'})
null

@baudehlo I think this is _kind of_ like what you want in
node-address-rfc2821? Just guessing.

jackbowman/email-addresses,FogCreek/email-addresses