Add getOpt function

Allows to get a previously set option.
Add unit tests
Added tests for getUrl method
Add getUrl, setUrl methods and setUrl call
Add call to setUrl in single requests
Add call to setUrl in other verbs
Split test for getUrl from test for getOptions
Add unit test for normal getUrl cases
Merge branch 'multiple-curl-info-callback' of https://github.com/matteo78/php-curl-class

* 'multiple-curl-info-callback' of https://github.com/matteo78/php-curl-class:
  Add unit test for normal getUrl cases
  Split test for getUrl from test for getOptions
  Add call to setUrl in other verbs
  Add call to setUrl in single requests
  Add getUrl, setUrl methods and setUrl call
  Added tests for getUrl method
  Add unit tests
  Add getOpt function
Include querystring data in the url for the appropriate HTTP request methods