It is rvalue already.
Json formatter placeholder added.
Custom mapping scheme has been refactored.

Now all custom mapping actions located in mapping namespace. Main class is mapper_t. User can define its own handlers and pass it to the mapper.
Expected type is also explicitly specified.
Benchmark fix.
Google tests are back.
Mock namespacing.
Exception trap has been implemented. Some bugs have been fixed.
Exception handler review.
Decomposition done.
More complex exception handler idiom has been implemented.

Now you can define expected exception types and provide own visitor for processing exceptions through its types. Exception catchers is built in compile-time.
Old-style is also available.
Exception trap test added.
Metafunction decomposition done.