provide help when initialization fails

added information (mainly) for people upgrading from version 1
when Savon::Client is initialized with e.g. a string.

fixes #365
revert "provide help when initialization fails"

This reverts commit 597c60d84569ec5f301e180ef5ca68f5f9b8c848.
provide help when initialization fails

added information (mainly) for people upgrading from version 1
when Savon::Client is initialized with e.g. a string.

fixes #365