Changed [<-.data.table to allow data.table-style indexing for i. Added test cases for [<-.data.table and $<-.data.table.
Changed [<-.data.table to allow data.table-style indexing for i. Added test cases for [<-.data.table and $<-.data.table.

jangorecki/data.table,vlulla/data.table,jangorecki/data.table,Rdatatable/data.table,Rdatatable/data.table,jangorecki/data.table,Rdatatable/data.table,vlulla/data.table,vlulla/data.table,jangorecki/data.table,vlulla/data.table,Rdatatable/data.table