fix #120 SVG on Safari, improve on other browsers

[kahboom]

Changes:

• Switch from image to inline SVG for faster rendering (no caching), easier cross-browser compatibility, and one less HTTP request.
• Remove unused classes.
• Adjustment of width/height in line with viewBox to ensure proper rendering.
• Mobile device-friendly.

Tested with latest versions of Chrome, Firefox, and Safari:

Mobile:

Still waiting on an open source license from BrowserStack to test on IE, hence adding the logo and hyperlink to the README as well:

fix #120

[pure-bot[bot]]

Pull request approved by @zregvart - applying approved label