mention Jinja in install docs
add jinja to optional dependencies in setup.py
Merge pull request #2839 from minrk/jinja

add jinja to install docs / setup.py
start introducing less
start to migrate to variables
start mixins
Revert "remove less.css"

This reverts commit 076a0fac5a12d4b674f2343f484a2c983a410219.
use less for tooltip
remove useless classes
main_app -> ipython-main-app
add less flag
generate style.css
less flag in templates
fix print css less
make file and other less
readd flexible-box-model
add default bootstrap theme
does not import code in bootstrap
recompile css
fix cell type selector css