Notes:

Current Version: 5.4.0

Decreased compile time and build size
Make "reflection" module built in (losing some of the time / build size gains)
Add new "class" syntax for ChaiScript defined methods and attributes see: unittests/class.chai for examples
Minor performance enhancements
major to_string performance enhancements
Provide API for retrieving registered type name #124
Added strong reference to container to range object #132

Add automatic conversion of arithmetic return types, following the same rules as conversion of arithmetic types when passing parameters
Add automatic casting up the inheritence hierarchy when possible.
Enable travis.ci testing
Allow users to add globals from within script
Various static analysis fixes
Code modernization to C++11
Unofficial support for Haiku added
Fix #121 - Inability to compile on cygwin
Formatting fixes and spelling corrections
Apply "include what you use" https://code.google.com/p/include-what-you-use/
Apply clang-modernize
Various threading fixes
Performance improvements

Official support for MSVC with C++11. All major platforms and compilers are now support for C++11 release

Enhanced unit tests
Add continue statement, fix various use cases for for loops
Fix use of suffixed numbers in vector initialization
Code cleanups
Eliminate global data, which makes code more portable and thread safe
Fix issue #79
Merge pretty_print fixes from @mgee #82
Compiler warning fixes for latest compiler releases
Fix threading problems
Fix linking error on MacOS Mavericks #88
Allow non-const globals
Make sure user cannot name a variable with :: in it #91
Fix various string / map / vector size and count calls for compilers which have weird overloads for them. #90 #93 #95
Make module search path relative to the currently running executable
Build and work with wstring windows builds
fix for some new line cases in the middle of a vector initialization from jespada

Add support for automatic conversion of arithmetic types when possible and when no ambiguous method dispatch exists.

svenstaro: Unused variables and CMake consistency fixes
Added support for returning pointers from functions (#13)
Compile with -pedantic (#9)
Fix issues with multiple ChaiScript object types having the same attribute name (#15)
Prevent variable redeclaration in same scope (#22)
mgee: Boxed_Number improvements (#27)
Support switch statements (#34)
Fix uint16 comparions (#26)
Add ability to add const_var globals in Module objects (#14)
Add support for ternary operators ?:
Add headers to CMakeLists so they show up in IDEs
Add ability to get vector of defined objects and vector of defined functions
Fix memory leak in cyclical references
Clean up static analysis issues discovered
Fix vector construction to be consistent with map construction
Increased unit tests to 161
Performance enhancements

Numeric operations performance increased approximately 10x
Looping operations performance increased up to 2x
Engine start up time decreased
Several parsing bugs related to index operators fixed
Added full support for all C algebraic types: double, long double, float, int, long, char, uint8_t, uint16_t, uint32_t, uint64_t, int8_t, int16_t, int32_t, int64_t
Enhanced support for capturing of exceptions thrown from ChaiScript in C++

Code simplifications
Fully integrate documentation with source code in doxygen style comments
Unit tests increased from 114 to 137
Automatic conversion between boost::function objects and ChaiScript functions
Many bug fixes
Minor performance improvements
Namespace reorganization to make end user code more accessible
clang support
VisualStudio 2010 Support
Support for C++ base classes and automatic upcasting
Remove __ reserved identifiers
Better code organization to reduce #ifdefs
clanmills: command line options for chai eval
clanmills: parser cleanups and code reduction
Function introspection and reflection
Correct function dispatch order to account for base classes and provide a defined order of dispatch
Predictable object lifetime that emulates C++ stack lifetime
emarcotte: pkgconfig support
standardize on method/member naming and indentation
64bit Visual Studio support
Better support for const objects
Drastic reduction of runtime exceptions - making debug builds orders of magnitude faster
Support for platforms with no loadable module support
Add helper macro for registering class