Update Logback version in README

Author: jxnu-liguobin

README.md

@@ -22,7 +22,7 @@ if (logger.isDebugEnabled) logger.debug(s"Some $expensive message!")
 A compatible logging backend is [Logback](http://logback.qos.ch), add it to your sbt build definition:
 
 ```scala
-libraryDependencies += "ch.qos.logback" % "logback-classic" % "1.5.21"
+libraryDependencies += "ch.qos.logback" % "logback-classic" % "1.4.14"
 ```
 
 If you are looking for a version compatible with Scala 2.10, check out Scala Logging 2.x.