Minify CSS and remove extraneous stuff, also added support for floating chat button

[MHambrick]

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/to cramforce dvoytenko

• extensions/amp-ngage-livechat/0.1/amp-ngage-livechat.css
• extensions/amp-ngage-livechat/0.1/amp-ngage-livechat.js
• extensions/amp-ngage-livechat/readme.md
• gulpfile.js

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