Updated APIs for 2.4.3

Zapv2.php
  - Add new classes
  - throws ZapError when sendRequest method returns False
Other PHP API files
  - Regenerated with the command "ant generate-apis" using
    the following PhpAPIGenerator.java in 'zaproxy' repository (branch 2.4.3)
    - Fix Issue 2108
    - Fix Issue 2168
PhpAPIGenerator.java (fixed on my local environment 'zaproxy' repository)
  - Fix Issue 2108
  - Fix Issue 2168

Modify the comment on Zapv2.php

Update almost all files for v2.4

Because I updated PhpAPIGenerator.java in the zaproxy repository and update PHP API class files by executing 'ant generate-apis'
command. And I also modified Zapv2.php to fit them.

Merge pull request #3 from yukisov/bugfix-exception

Improve Usage in README.md

Fixed some methods

Because some methods were generated from zaproxy trunk not from zaproxy branch
2.3.

Fixed the license notation for Apache License, Version 2.0

Bugfix: Issue 1251 : Client API doesnt set the apikey

Add authors' email in composer.json

Change the vendor name of its own

Improve Zapv2::statusCode($url) method

Get the proxy value of stream at the beginning and put it back in the place
after the main task is done.