Updates to projects page
Minor modifications; added new post

- Now using the latest version of Jekyll by default.
- The current time isn't necessary in the YAML front matter.
- Removed a reference used in the "Creating graphs in Ruby" post.
- Added a post about cross validation in Ruby.
- Added a plugin (jekyll-scholar) to build references in my posts.
- And finally, a fix to the `.center` class in the LESS files.