updated CHANGELOG.md for 0.4.0 release

CHANGELOG.md

 Embedded Multicore Building Blocks (EMB²)
 =========================================
 
+
+Version 0.4.0
+-------------
+
+### Features:
+- Added consistency checking functionality to dataflow
+- Added C++ wrapper for base_c logging functions
+- Reworked dataflow_cpp interface for easier usage
+
+### Changes and improvements:
+- Improved network plugin with better error checking and task cancelation support
+- dataflow_cpp network token count is now set at runtime
+- Added automatic determination of token count to dataflow_cpp
+- All C interface functions check pointers for NULL
+- mtapi_info_t conforms to the standard
+- Fixed CodeSonar warnings across the code base
+- Spinlocks yield every 1024 spins now
+- Changed asserts on interface visible parameters to execeptions
+
+### Bug fixes:
+- Fixed problem causing low performance on the Jetson TK1 board
+- Fixed bug in mtapi_c causing a task wait to hang
+- Fixes issue with the AMD APP SDK in the OpenCL plugin
+- Fixed problem with automatic initialization in tasks_cpp
+- Fixed memory leaks in tests
+
+### Build system:
+- Dependency on an installed OpenCL SDK was removed
+- Moved all MTAPI plugins into folder mtapi_plugins_c
+
+### Documentation:
+- Updated README to reflect new directory structure
+- Updated DoxyGen documentation of dataflow_cpp for the improved interface
+- Updated tutorial and examples to show the usage of dataflow_cpp
+
+
 Version 0.3.2
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