added blackboxing doc and blackboxing assets
removed needless images. added note about filing a bug at bottom
Merge github.com:GoogleChrome/devtools-docs into blackboxing

* github.com:GoogleChrome/devtools-docs:
  Improve formatting of contributing.md
  Fix typo
  Update remote-debugging.html
combine call stack screens
combine context menu screens
Merge github.com:GoogleChrome/devtools-docs into blackboxing

* github.com:GoogleChrome/devtools-docs:
  Quick fix on image for homepage to bypass cache
Merge pull request #162 from jaredwilli/blackboxing

Added blackboxing doc and blackboxing assets