Fix README Kotlin version

Author: bnorm

README.md

@@ -74,7 +74,7 @@ Builds of the Gradle plugin are available through the
 
 ```kotlin
 plugins {
-  kotlin("jvm") version "1.3.70"
+  kotlin("jvm") version "1.4.0"
   id("com.bnorm.power.kotlin-power-assert") version "0.4.0"
 }
 ```
@@ -93,7 +93,7 @@ configure<com.bnorm.power.PowerAssertGradleExtension> {
 ## Kotlin IR
 
 Using this compiler plugin only works if the code is compiled using Kotlin
-1.3.70 and IR is enabled. IR can be enabled only when compiling the test
+1.4.0 and IR is enabled. IR can be enabled only when compiling the test
 SourceSet if desired. As Kotlin IR is still experimental, mileage may vary.
 
 ```kotlin