Added html-proofer dependency

To use for validating HTML output
Added Rakefile

Enables rake test to run html-proofer
Enabled utf-8 encoding in _config.yml

Jekyll build was not reading the markdown files as utf-8
causing the build to fail.
Fixed invalid url in page

Invalid url was causing html-proofer error
Added alt text for image

html-proofer was raising errors due to lack of alt text for image.
html spec requires alt text for all images.
Added dashes to header

To have yaml correctly detected.
Fixed invalid url

url invalid due to missing forward slash in http://
Renamed files to remove spaces

html-proofer raises "page does not exist" error for filenames
with spaces.
Corrected invalid url

Path in url was incorrect causing 404
Added index.html to participant directory

html-proofer raises invalid internal link error if no index.html
file is found.
Changed url

External path to image times out. Changed path to internal absolute
so assuming a permissions issue on participant directory or file.
Externally navigating to other participant image files does not
error.
Added exclude vendor directory

Travis bundles gems in vendor directory on server. Jekyll will
read this and explode. Excluding vendor directory avoids this.
Added .travis.yml file for use with Travis-CI

Added basic file with no special parameters in order to begin
automated tests with Travis CI.
Added rake gem as a dependency
rake auto added to Gemfile.lock
Added travis branch to .travis.yml

Hopefully this forces Travis CI test automation on this branch
Removed reference to cibuild script
Made the :default Rakefile task run :test
Updated gems
Commented out Nokogiri

Testing to see if this corrects html parse issue