feat: ES 1.6.0 compatiblity check

adding travis check for ES 1.6.0

docs: 1.5.0 compatiblity with ES 1.6.x

Author: emiguez

.travis.yml

@@ -5,6 +5,7 @@ env:
   - ES_VERSION=1.5.0
   - ES_VERSION=1.5.1
   - ES_VERSION=1.5.2
+  - ES_VERSION=1.6.0
 cache:
   directories:
     - $HOME/.m2

README.md

@@ -18,7 +18,7 @@ There is no way to configure this on a per index basis.
 
 |     Http Basic Plugin       | elasticsearch         |
 |-----------------------------|-----------------------|
-| v1.5.0(master)              | 1.5.x                 |
+| v1.5.0(master)              | 1.5.x, 1.6.x          |
 | v1.4.0                      | 1.4.0                 |
 | v1.3.0                      | 1.3.0                 |
 | v1.2.0                      | 1.2.0                 |