Add a configuration to use custom URL validation.

[erozqba]

Fix #37

• Add a configuration option to allow a non-standard URL for ticket validation.

[erozqba]

Hi XavRsl,
Any comments and suggestions are appreciated. I'm no pretty sure if the comments are more helpful now but I will happily apply any changes you suggest.

Is a lot more clear for me now when use phpCAS::setServerProxyValidateURL, phpCAS::setServerServiceValidateURL or phpCAS::setServerSamlValidateURL after reading the CAS protocol specifications https://apereo.github.io/cas/5.0.x/protocol/CAS-Protocol-Specification.html

I will suggest a correction to the example https://github.com/Jasig/phpCAS/blob/master/docs/examples/example_custom_urls.php because the comments are confusing and suggest that the setServerProxyValidateURL is for CAS 2.0 and phpCAS::setServerServiceValidateURL is for CAS 1.0 but is not what the specification says.

[erozqba]

Hi XavRsl,
The PR #216 in phpCAS apereo/phpCAS#216 has been accepted, could you review this patch and give me a feedback? Thanks in advance and happy new year 2017!