Load jsapi using https instead of http

to fix the error from chrome browser
~~~
[blocked] The page at 'https://ankane.github.io/chartkick.js/examples/' was loaded over HTTPS, but ran insecure content from 'http://www.google.com/jsapi': this content should also be loaded over HTTPS.
 ankane.github.io/:1
[blocked] The page at 'https://ankane.github.io/chartkick.js/examples/' was loaded over HTTPS, but ran insecure content from 'http://ajax.googleapis.com/ajax/libs/jquery/1.9.1/jquery.min.js': this content should also be loaded over HTTPS.
~~~