General updates

* Remove hardcoded SSLv3 and let SSL autodecide again ( fixes https://github.com/thybag/PHP-SharePoint-Lists-API/issues/65 )
* Fix incorrect namespace (+ add copyright info) to streamwrapper (fixes https://github.com/thybag/PHP-SharePoint-Lists-API/issues/61 )
* Add deleteAttachment method as contributed by @jjworld https://github.com/thybag/PHP-SharePoint-Lists-API/issues/57
* Improve auth fail for SPOnline
* remove `getItemVersion` as this feature didn't work correctly (see #55 & #54 for some further info)