Get rid of Bootstrap

[xferra]

Bootstrap is used only for grid layout = other lightweight lib or custom style will be better in terms of performance and page size.

Links for additional investigation, just FYI:

• Keep the Web Open with Cross-Browser Testing
• Optimize CSS Delivery
• W3 Validators
• Make the Web Work For Everyone
• Google's opinionated reference for building amazing web experiences
• Accelerated Mobile Pages
• MDN: Design and accessibility
• CSS Grids
• 12 Small CSS Frameworks (Cache)
• Critical Rendering Path

Part of generic Optimization issue #39