Create new Gemfile.lock to reflect latest Gem releases

Gem update of interest includes Jekyll 1.1.0, leaping
from the 0.12 release previously reflected in the
Gemfile.lock.
remove old vendor/cache for new jekyll stuff
have to ignore gems now because of jekyll 1.0 being cached
Add placeholder/temp text to otherwise empty slide

Jekyll processing of slide markdown with only a
Liquid capture block fails to correctly build.

Temporary fix is to include placeholder text
prior to the {% capture notes %} line.
Merge pull request #173 from github/gem-updates

Create new Gemfile.lock to reflect latest Gem releases