[CSV-255] Add CSVRecord.isSet(int) method apache#52.

Less cryptic parameter name.

Author: garydgregory

src/main/java/org/apache/commons/csv/CSVRecord.java

@@ -217,12 +217,12 @@ public boolean isSet(final String name) {
     /**
      * Checks whether a column with given index has a value.
      *
-     * @param i
+     * @param index
      *         a column index (0-based)
      * @return whether a column with given index has a value
      */
-    public boolean isSet(final int i) {
-        return 0 <= i && i < values.length;
+    public boolean isSet(final int index) {
+        return 0 <= index && index < values.length;
     }
 
     /**