Change thumbnail default size and resize algorithm (#336)

* Change thumbnail resize algorithm and add size parameter

* Height -> Width

* Change default size from 100px to 200px

* Height -> width

pkg/manager/running_streams.go

@@ -9,7 +9,7 @@ import (
 )
 
 var (
-	streamingFiles = make(map[string][]*http.ResponseWriter)
+	streamingFiles      = make(map[string][]*http.ResponseWriter)
 	streamingFilesMutex = sync.RWMutex{}
 )