Fixed mobile chrome bug for rich text editor

This PR modifies Gemfile to point bootstrap-wisihtml5 gem installation to my git repo. 

Previous check IOS function: 
1. Check whether it is webkit and 
2. Check IOS version to be greater than 0. 
=> Chrome mobile fails passes the first check but fails the second check as it uses webkit but it is not IOS. 

New gem rectifies the check IOS function and allows mobile chrome to work.

I will submit the suggested change to original open source git repo. If they accept my changes, we can rectify gemfile to point back to original gem.