Grand test fixup (#138)

* start fixing up tests

* fix up tests + automate with drone

* fiddle with linting

* messing about with drone.yml

* some more fiddling

* hmmm

* add cache

* add vendor directory

* verbose

* ci updates

* update some little things

* update sig

vendor/github.com/dsoprea/go-exif/v2/undefined/registration.go

@@ -0,0 +1,42 @@
+package exifundefined
+
+import (
+	"github.com/dsoprea/go-logging"
+)
+
+// UndefinedTagHandle defines one undefined-type tag with a corresponding
+// decoder.
+type UndefinedTagHandle struct {
+	IfdPath string
+	TagId   uint16
+}
+
+func registerEncoder(entity EncodeableValue, encoder UndefinedValueEncoder) {
+	typeName := entity.EncoderName()
+
+	_, found := encoders[typeName]
+	if found == true {
+		log.Panicf("encoder already registered: %v", typeName)
+	}
+
+	encoders[typeName] = encoder
+}
+
+func registerDecoder(ifdPath string, tagId uint16, decoder UndefinedValueDecoder) {
+	uth := UndefinedTagHandle{
+		IfdPath: ifdPath,
+		TagId:   tagId,
+	}
+
+	_, found := decoders[uth]
+	if found == true {
+		log.Panicf("decoder already registered: %v", uth)
+	}
+
+	decoders[uth] = decoder
+}
+
+var (
+	encoders = make(map[string]UndefinedValueEncoder)
+	decoders = make(map[UndefinedTagHandle]UndefinedValueDecoder)
+)