Add support for gchart's newer library loader#113

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cmtjk wants to merge 3 commits intoagiliq:masterfrom

cmtjk:Support_for_gchart_loader_js

Commits on Mar 6, 2017

Added possibility to use gchart with its preferred library loading method.
Cornelius Matějka
committed

Commits on Mar 7, 2017

Added warning when using old jsapi loader.
Cornelius Matějka
committed
Updated README.md gchart examples according to the newer and preferred gstatic library loader.
Cornelius Matějka
committed