travis: use mono 4.8.0

ethomson · ethomson · commit 576232eb3ca5 · 2017-06-13T14:36:32.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -3,7 +3,7 @@
 
 language: csharp
 mono:
- - latest
+ - 4.8.0
 
 os:
  - osx

-Original file line number
+Diff line change
 language: csharp
 mono:
 - - latest
 + - 4.8.0
 os:
  - osx