Project structure refactor:

- Change package name general_server to gateway
- Changing the structure of directories and packages
- Adding vendor to the project

vendor/gopkg.in/natefinch/lumberjack.v2/.travis.yml

@@ -0,0 +1,11 @@
+language: go
+
+go:
+  - tip
+  - 1.15.x
+  - 1.14.x
+  - 1.13.x
+  - 1.12.x
+  
+env:
+  - GO111MODULE=on