Started writing documentation and adding examples

csv.go

@@ -6,6 +6,10 @@ import (
 	"io"
 )
 
+// CSVColumn is a filter function that reads the source as a CSV file and extracts the cell
+// values of the named column, excluding the header itself. If the column cannot be found,
+// the filter will produce nothing. If the column index is beyond the number of columns
+// for a particular row, it will be skipped.
 func CSVColumn(name string) func(r io.Reader, w io.Writer) error {
 	return func(r io.Reader, w io.Writer) error {
 		cr := csv.NewReader(r)