Adding option to set Guzzle requests timeout

Related to #205 added option to set Guzzle requests if needed.
Also, includes fix to remove use of 'function' keyword for compatibility with symfony 2.7 and fix issue with rate limit header unit test failing

Adding rate limit header info

This allows users to access rate limit info contained in the rate limit headers in the response.

v3.1.4: Merge pull request #229 from intercom/readme_update

Updating for new view segment option

v3.1.2

Several fixes to phpdocs, contributed by @fnwbr @andrewandante

v3.0.2

Add PhpDoc to methods and variables
Add a new method to IntercomUsers to allow fetching details of a single user by its Intercom id

v3.0.1

Add method for deleting a user

v3.0.0

• Requires php 5.6 (which is why we are using a major version)
• Fixes an issue were Notes where not available. Thanks to @512banque for the fix.
• Readme improvements

v2.0.0

Major rewrite using recent Guzzle

v1.5.0

Adds created_since when listing users

v1.4.0

Adds order when listing users