Design group_concat_columns API, thx @ukisami for this tip
implement calculate group_concat
Fix add group_concat column
Add `always` DSL and related
Remove statlysis/cron/count/dimensions related
Use Mysql2::Client to create statlysis database
convert [:user_id] to [{:column_name => :user_id, :type => :integer}]
Compact setup database with mysql and sqlite, add group_by columns & indexes
Use Timely as parent instead of Count, subclasses are OneDimension and MultipleDimension, all tests are passed
auto judge dimension in Timely
Support for whether time_column exists in dimensions or not
Add & apply TimeUnitToTableSuffixHash
Dont index :t if not exist
Explain a situation that statistics without time_column
Add "In Mongodb, why use MapReduce instead of Aggregation?".QA
Sort insert values in test
cron.output should is a Enumerable
Add CodeGistMongoid.model & prepare data
Implement Timely#multiple_dimensions_output_without_time_column
Fix creating stat table in different situations