added IResponse::getHeader() (BC break)
static Response::date() moved to Helpers::formatDate()
avoid using magic methods
Request: raw body is now passed as callback via constructor
added test for Request::detectLanguage
Session: fixed not respecting its own and IResponse's API
Request: deprecated useless method isPost()
Request: default method is GET
Request: unified getRemoteHost() conditions
Request: refactored getHeader()
improved phpDoc
typo
Merge pull request #19 from JanTvrdik/improvements

Few improvements and bugfixes
IRequest: methods getQuery(), getPost(), getFile() and getCookie() can accept multiple keys (BC break)