Implementing generic parser plugins and documentation

This constitutes a large change in how we will parse different data
formats going forward (for the plugins that support it)

This is working off @henrypfhu's changes.

internal/internal.go

@@ -9,7 +9,6 @@ import (
 	"fmt"
 	"io/ioutil"
 	"os"
-	"strconv"
 	"strings"
 	"time"
 )
@@ -35,47 +34,6 @@ func (d *Duration) UnmarshalTOML(b []byte) error {
 
 var NotImplementedError = errors.New("not implemented yet")
 
-type JSONFlattener struct {
-	Fields map[string]interface{}
-}
-
-// FlattenJSON flattens nested maps/interfaces into a fields map
-func (f *JSONFlattener) FlattenJSON(
-	fieldname string,
-	v interface{},
-) error {
-	if f.Fields == nil {
-		f.Fields = make(map[string]interface{})
-	}
-	fieldname = strings.Trim(fieldname, "_")
-	switch t := v.(type) {
-	case map[string]interface{}:
-		for k, v := range t {
-			err := f.FlattenJSON(fieldname+"_"+k+"_", v)
-			if err != nil {
-				return err
-			}
-		}
-	case []interface{}:
-		for i, v := range t {
-			k := strconv.Itoa(i)
-			err := f.FlattenJSON(fieldname+"_"+k+"_", v)
-			if err != nil {
-				return nil
-			}
-		}
-	case float64:
-		f.Fields[fieldname] = t
-	case bool, string, nil:
-		// ignored types
-		return nil
-	default:
-		return fmt.Errorf("JSON Flattener: got unexpected type %T with value %v (%s)",
-			t, t, fieldname)
-	}
-	return nil
-}
-
 // ReadLines reads contents from a file and splits them by new lines.
 // A convenience wrapper to ReadLinesOffsetN(filename, 0, -1).
 func ReadLines(filename string) ([]string, error) {