Update image paths in Readme

I updated the image URLs to use `raw.github.com`.

Fixes #81
Merge branch 'source/master'

# By Chris Schmitz
# Via Ryan Bigg
* source/master:
  Update image paths in Readme
Removed annoying admin tab
Merge branch 'master' into 2-0-stable

# By Chris Schmitz (1) and Jim (1)
* master:
  Removed annoying admin tab
  Update image paths in Readme