Use String#include? instead of end_with? to avoid message duplication
Use String#include? instead of end_with? to avoid message duplication

Previously, did_you_mean used `msg.end_with?(suggestion)` to check if
its suggestion is already added.

I'm now creating a gem that also modifies Exception's message. This
breaks did_you_mean's duplication check.
This change makes the check use String#include? instead of end_with?.

yuki24/did_you_mean