Create zh-cn.po

starting a simplified chinese translation
Update zh-cn.po
Add money description strings
Merge branch 'master' into chinese
fall back to English when translation string is empty
add a Makefile target that extracts i18n messages
don't use interpolation so the messages can be automatically extracted
use a syntax for plurals that works with automatic message extraction
ran `make i18n_update`
blank out missing translations
turn off fuzzy matching
finish wrapping messages for i18n in `templates/base.html`
complete the i18n of four templates
wrap the messages in `templates/support-gittip.html` for i18n
remove trailing zeros
use "$" instead of "$US" as the USD symbol in French
make i18n_update
localize country names
get rid of the "None" message
remove punctuation so the message is the same we use elsewhere