Strict mode error

Declaration of Redmine\Api\SimpleXMLElement::addChild() should be compatible with SimpleXMLElement::addChild($name, $value = NULL, $ns = NULL)
Update Group.php

Corrected bug in addUser. '/groups/'.$id.'/users.xml' instead of '/groups/'.$id.'/user/users.xml'. Tested and it works
added test case for validateSharing in versions API
added tests for buildXML of membership API
added tests for create and update of issue category API
added tests for addWatcher and removeWatcher of issue API
fixed removeWatcher in issue API
added missing covers annotation and test case
added test case for TestUrlClient
added test for cleanParams and create of issue API
added test for update of issue API
fixed setPort if no port or scheme is detected
Merge pull request #70 from GuyFawkes/patch-2

Strict mode error
Merge pull request #72 from BertaOctech/berta

Update Group.php. Bug in addUser solved
Merge pull request #73 from JanMalte/unittests

added some more Unittests to reach higher code coverage
Merge pull request #74 from JanMalte/patch-1

fixed setPort if no port or scheme is detected
fix group - user tests
update readme + add phpunit to composer + remove un-needed docblocks from tests
cast port to int
Replaced PHP_EOL with "\n", fixes tests on windows [#75]