Merge pull request #38 from Carreau/ga

enable google analytics
add nbcv2submodule
update sm
new nbviewer from jinja branch
update submodule
improve toolbar css
enable GA, comment unused JS
fix download notebook
small easter eggs/nbviewer themes

By tempering with the cookie, you can force a theme to be
applied to a notebook  :-)
use tornado as WSGI, and improve cache
use sasl memcached with falsk-cache
del cachedfirst param
def min/hours un cachedget
caches only inner body
caches errors and popular
remove /popular url and stats

with recent improvement, db is the bottleneck
pylinting
fix css output pre
renable theme selection
add FAQ