Added section on union data sources
Merge branch 'master' into fix-datasource-doc
fixed typo and added info that union can take any number of dataSources
Merge branch 'master' into fix-datasource-doc
fixed typo, added note on matching schema requirement for unioned data sources
Merge pull request #814 from metamx/fix-datasource-doc

Added section on union data sources
Merge branch 'master' of github.com:metamx/druid into druid-0.7.x
Merge branch 'druid-0.7.x' of github.com:metamx/druid into druid-0.7.x
add encoding