guzzlehttp/guzzle version dependency

[anurag-cohaesus]

I am trying to use this with the latest Drupal version and composer update is giving me these errors.

Problem 1
- Can only install one of: guzzlehttp/guzzle[6.2.1, 5.3.x-dev].
- Can only install one of: guzzlehttp/guzzle[6.2.2, 5.3.x-dev].
- Can only install one of: guzzlehttp/guzzle[6.2.3, 5.3.x-dev].
- Can only install one of: guzzlehttp/guzzle[6.3.0, 5.3.x-dev].
- Can only install one of: guzzlehttp/guzzle[6.3.1, 5.3.x-dev].
- Can only install one of: guzzlehttp/guzzle[6.3.2, 5.3.x-dev].
- Can only install one of: guzzlehttp/guzzle[6.3.3, 5.3.x-dev].
- Can only install one of: guzzlehttp/guzzle[6.3.x-dev, 5.3.x-dev].
- Can only install one of: guzzlehttp/guzzle[5.3.x-dev, 6.3.3].
- ianchadwick/maxcontact dev-master requires guzzlehttp/guzzle ~5.0 -> satisfiable by guzzlehttp/guzzle[5.3.x-dev].
- Installation request for ianchadwick/maxcontact dev-master -> satisfiable by ianchadwick/maxcontact[dev-master].
- Installation request for guzzlehttp/guzzle ^6.2.1 -> satisfiable by guzzlehttp/guzzle[6.2.1, 6.2.2, 6.2.3, 6.3.0, 6.3.1, 6.3.2, 6.3.3, 6.3.x-dev].

I would request to update the guzzle package version to the latest i.e.

"guzzlehttp/guzzle": "~6.0"