Import source: handler/content

Import the existing local project snapshot. This commit organizes existing files; it does not represent newly developed functionality.

handler/content.go

@@ -0,0 +1,8 @@
+package handler
+
+// ContentHandler defines an interface for handling content sources that are
+// represented as URLs. When the handler will finish its job it should notify
+// the progress. Each error should be sent to the errors channel.
+type ContentHandler interface {
+	Process(url string, progress chan<- int, errors chan<- error)
+}