output: display key in filtered output for csv, column and table

Fixes #63

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>
diff --git a/cmd/output.go b/cmd/output.go
index 63b4404..91c434d 100644
--- a/cmd/output.go
+++ b/cmd/output.go
@@ -175,7 +175,7 @@
 	}
 }
 
-func filterResponse(response map[string]interface{}, filter []string) map[string]interface{} {
+func filterResponse(response map[string]interface{}, filter []string, outputType string) map[string]interface{} {
 	if filter == nil || len(filter) == 0 {
 		return response
 	}
@@ -195,11 +195,19 @@
 				}
 				filteredRow := make(map[string]interface{})
 				for _, filterKey := range filter {
+					if len(strings.TrimSpace(filterKey)) == 0 {
+						continue
+					}
 					for field := range row {
 						if filterKey == field {
 							filteredRow[field] = row[field]
 						}
 					}
+					if outputType == config.COLUMN || outputType == config.CSV || outputType == config.TABLE {
+						if _, ok := filteredRow[filterKey]; !ok {
+							filteredRow[filterKey] = ""
+						}
+					}
 				}
 				filteredRows = append(filteredRows, filteredRow)
 			}
@@ -214,7 +222,7 @@
 }
 
 func printResult(outputType string, response map[string]interface{}, filter []string) {
-	response = filterResponse(response, filter)
+	response = filterResponse(response, filter, outputType)
 	switch outputType {
 	case config.JSON:
 		printJSON(response)
diff --git a/config/about.go b/config/about.go
index b603ff2..c2a4384 100644
--- a/config/about.go
+++ b/config/about.go
@@ -26,7 +26,7 @@
 
 // Version CLI
 func (c *Config) Version() string {
-	return "6.1.0-alpha"
+	return "6.1.0"
 }
 
 // PrintHeader prints startup message in CLI mode