remove concept of prod and dev assets

instead always do the "prod" thing, but use entr for restarting the
server for all assets

server/assets_getters.go

@@ -0,0 +1,27 @@
+package server
+
+import (
+	"bytes"
+	"errors"
+	"io"
+	"time"
+)
+
+var errAssetNotFound = errors.New("asset not found")
+
+func findAsset(path string) (time.Time, io.ReadSeeker, error) {
+	asset, ok := assetBytes[path]
+	if !ok {
+		return time.Time{}, nil, errAssetNotFound
+	}
+	reader := bytes.NewReader(asset.Bytes)
+	return asset.ModTime, reader, nil
+}
+
+func findAssetBytes(path string) (time.Time, []byte, error) {
+	asset, ok := assetBytes[path]
+	if !ok {
+		return time.Time{}, nil, errAssetNotFound
+	}
+	return asset.ModTime, asset.Bytes, nil
+}