Add Etcd4j as a new Java client option

Documentation/clients-matrix.md

@@ -28,6 +28,7 @@ Sorted alphabetically on language/name
 |[clj-etcd](https://github.com/rthomas/clj-etcd)                  |Clojure|-|-|G|G|-|B|-|-|
 |[etcd-clojure](https://github.com/aterreno/etcd-clojure)         |Clojure|-|-|F|F|F|F|-|-|
 |[go-etcd](https://github.com/coreos/go-etcd)                     |go     |Y|Y|F|F|F|F|-|-|
+|[etcd4j](https://github.com/jurmous/etcd4j)                      |java   |Y|Y|F|F|F|F|-|-|
 |[jetcd](https://github.com/diwakergupta/jetcd)                   |java   |Y|-|B|B|-|B|-|-|
 |[Etcd.jl](https://github.com/forio/Etcd.jl)                      |Julia  |-|-|F|F|F|F|Y|Y|
 |[etcetera](https://github.com/drusellers/etcetera)               |.net   |-|-|F|F|F|F|-|-|

Documentation/libraries-and-tools.md

@@ -15,6 +15,7 @@
 
 - [justinsb/jetcd](https://github.com/justinsb/jetcd)
 - [diwakergupta/jetcd](https://github.com/diwakergupta/jetcd) - Supports v2
+- [jurmous/etcd4j](https://github.com/jurmous/etcd4j) - Supports v2
 
 **Python libraries**