update es to 5.4.0 (#369)

README.md

@@ -11,6 +11,7 @@ Versions
 IK version | ES version
 -----------|-----------
 master | 5.x -> master
+5.4.0| 5.4.0
 5.3.2| 5.3.2
 5.2.2| 5.2.2
 5.1.2| 5.1.2

pom.xml

@@ -12,7 +12,7 @@
     <inceptionYear>2011</inceptionYear>
 
     <properties>
-        <elasticsearch.version>5.3.2</elasticsearch.version>
+        <elasticsearch.version>5.4.0</elasticsearch.version>
         <maven.compiler.target>1.8</maven.compiler.target>
         <elasticsearch.assembly.descriptor>${project.basedir}/src/main/assemblies/plugin.xml</elasticsearch.assembly.descriptor>
         <elasticsearch.plugin.name>analysis-ik</elasticsearch.plugin.name>