* fix(request strategy): always use XHR first then switch to fallback

    + add fallback for client.search

    Context: before this commit, when a user lost connectivity (or XHR was
    blocked, we cannot distinguish those events in browsers) then we
    forced using JSONP for the whole session.

    This led to a bug where you were stuck in a loop of non-available
    fallback even if connectivity was restored.

    This commit fixes this bug by always trying XHRS and fallbacking to
    JSONP on a per request basis.
  * refactor(map): use lodash map instead of custom fn