Update the javadoc link (#906)

Author: bullet-tooth

exonum-light-client/README.md

@@ -16,8 +16,7 @@ By using the client you are able to perform the following operations:
 - Receive blockchain blocks information 
 - Receive node system information 
 - Receive node status information  
-<!-- TODO: replace by javadoc link when it will be available --> 
-_*Please refer to [the code][exonum-client] for details._  
+_*Please refer to [the documentation][exonum-client] for details._  
 Also, see [examples](#examples). 
 
 ## Compatibility
@@ -139,4 +138,4 @@ Apache 2.0 - see [LICENSE](../LICENSE) for more information.
 [protobuf]: https://developers.google.com/protocol-buffers/docs/proto3
 [standard-serializers]: https://exonum.com/doc/api/java-binding-common/0.6.0/com/exonum/binding/common/serialization/StandardSerializers.html
 [send-tx-it]: ./src/test/java/com/exonum/client/ExonumHttpClientIntegrationTest.java
-[exonum-client]: ./src/main/java/com/exonum/client/ExonumClient.java
+[exonum-client]: https://exonum.com/doc/api/java-light-client/0.2.0/com/exonum/client/ExonumClient.html