Use new readitlater domain, when submitting pages

https://github.com/vimpr/vimperator-plugins/pull/44 addressed the change
of domain from 'readitlaterlist.com' to 'getpocket.com', but missed this
case.
Search for getpocket logins under https domain

getpocket.com is served via HTTP and HTTPS. Therefore, users may have
their credentials stored under both endpoints. Both should be checked.