add syntax highlighting

Author: memoizr

README.md

@@ -2,7 +2,7 @@
 AssertK provides a Kotlin-friendly syntax for using the amazing AssertJ assertion framework.
 
 ###Simple assertions
-```
+```kotlin
 assert that Unit isEqualTo Unit
 assert that Any() isNotEqualTo Any()
 assert that Any() _is notNull
@@ -12,12 +12,12 @@ assert that Any() describedAs "A labeled object" isInstance of<Unit>()
 ```
 
 ###Chained syntax
-```
+```kotlin
 assert that Unit isNotEqualTo Any() isEqualTo Unit _is notNull isInstance of<Any>()
 ```
 
 ###Block syntax
-```
+```kotlin
 assert that Any() isSuchThat {
     it _is notNull
     it isInstance of<Any>()
@@ -28,12 +28,12 @@ assert that Any() isSuchThat {
 
 ##Assertions on exceptions
 ###Chained syntax
-```
+```kotlin
 assert thatExceptionIsThrownBy { failFunction() } hasMessageContaining "foo" hasCause Throwable()
 ```
 
 ###Block syntax
-```
+```kotlin
 assert thatExceptionIsThrownBy {
     throw Throwable("exception foo", Throwable())
 } and {
@@ -47,7 +47,7 @@ assert thatExceptionIsThrownBy {
 ```
 
 ##Get it
-```
+```groovy
 allprojects {
     repositories {
         ...