clean old backend organization
filters and options
projectors and response data
array of filter values and new options
support groupby
change return options
change the argument style of projector and return
aggregation hub
aggregations
separate debug and production scripts
address #17#issuecomment-34572592
replace ≧
default return nothing: avoid excessive return upon tests
allow cross origin
clean backend
Merge pull request #26 from hxu/backend-pandas

Backend pandas
Merge branch 'master' into frontend