add yarn.lock parser (fanal#16)

* add yarn.lock parser

* skip analyze package files in dependency folder

analyzer/library/npm/npm.go

@@ -3,6 +3,7 @@ package npm
 import (
 	"bytes"
 	"path/filepath"
+	"strings"
 
 	"github.com/knqyf263/fanal/analyzer"
 	"github.com/knqyf263/fanal/extractor"
@@ -28,6 +29,11 @@ func (a npmLibraryAnalyzer) Analyze(fileMap extractor.FileMap) (map[analyzer.Fil
 			continue
 		}
 
+		// skip analyze files which in dependency folder
+		if utils.StringInSlice(utils.NODE_DEP_DIR, strings.Split(filename, utils.PathSeparator)) {
+			continue
+		}
+
 		r := bytes.NewBuffer(content)
 		libs, err := npm.Parse(r)
 		if err != nil {