Merge pull request #5 from StableLib/go12

Drop support for Go 1.0 and 1.1.

.travis.yml

@@ -1,8 +1,7 @@
 language: go
 
 go:
-  - 1.0
-  - 1.1
   - 1.2
   - 1.3
+  - 1.4
   - tip

uniuri.go

@@ -78,5 +78,4 @@ func NewLenChars(length int, chars []byte) string {
 			}
 		}
 	}
-	panic("unreachable")
 }