Healthcenter update

If player tries to enter healthcenter without all three keys, Sahiya prompts her about the importance of the next key and asks her to obtain it. Upon getting all three keys, Sahiya prompts user that now she can enter the healthcenter. 

Closes #10 
Where is Q.Sahiya class defined now? Considering that you removed the class from javascript_people.js, did you define it somewhere else now and forgot to add it in commit?