Drop support for Go 1.10

This is necessary for the adoption of Go modules.
We still support the two latest versions of Go (min 1year).

Author: campoy

.travis.yml

@@ -1,7 +1,6 @@
 language: go
 
 go:
-    - "1.10"
     - "1.11"
     - "1.12"
 

README.md

@@ -52,7 +52,7 @@ few months. The [Changelog] is kept fairly up-to-date.
 ## Getting Started
 
 ### Installing
-To start using Badger, install Go 1.8 or above and run `go get`:
+To start using Badger, install Go 1.11 or above and run `go get`:
 
 ```sh
 $ go get github.com/dgraph-io/badger/v2/...