support UTF encoding for jekyll

@johnwunder @gtback 
This fixes an issue where jekyll 1.5.1 would not build the source docs locally due to the use of fancy >> characters in some source files.

i.e. `bundle exec jekyll build` =>
` Error reading file /home/dstar/Applications/stixproject.github.io/data-model/1.0.1/index.md: "\xE2" on US-ASCII`

Likely a non-blocking change, since it builds on github fine either way.