css tweaks

-jekyll base-url
- add "logo"
- clean up css
first draft of homepage

- add workflow image
re-add bootstrap.css

as github pages is not jekyll 2 yet and therefore does not support SASS
relative path to make it work with github.io/subdir
add link to generated website in README
Merge pull request #2 from Bio-Commons/topics/jekyll-config-and-setup

Topics/jekyll config and setup