Update README with reference to GPMueller/trace.

Author: GPMueller

README.md

@@ -3,6 +3,8 @@ Proper, portable exception handling with backtracing in C++11
 
 [![Build Status](https://api.travis-ci.org/GPMueller/mwe-cpp-exception.svg?branch=master)](https://travis-ci.org/GPMueller/mwe-cpp-exception)
 
+**See [GPMueller/trace](https://github.com/GPMueller/trace) for a proper exception backtracing library.**
+
 This MWE shows how [`std::nested_exception`](http://en.cppreference.com/w/cpp/error/nested_exception) and [`std::throw_with_nested`](http://en.cppreference.com/w/cpp/error/throw_with_nested) can be applied in order to not lose information while propagating
 an original `std::exception` upwards through a chain of function calls and create a **backtrace** without any overhead (compare e.g. logging of debug messages).
 This avoids much of the need for any debugging and provides a way of ensuring that a library does not crash ungracefully.
@@ -34,4 +36,4 @@ cmake --build .
 TODO
 --------------------------------------------------------------------
 - Extend this MWE with example exceptions which do not require the code to terminate.
-- Create unit tests with catch, using e.g. `REQUIRE_THROWS`
+- Create unit tests with catch, using e.g. `REQUIRE_THROWS`