fixed bug in missing parameter reporting
added functionable test
adding new function, return a
potentially fixed issue with promise evaluation, and removed return_a
fixed a bug with a misnamed missing function, and an issue with deparsing values
added tryCatch to require_a force function
updated news, and added a test for functionable
added a test for variadic functions, and fixed tests
added a test for variadic functions, and fixed tests
added support for negation traits
updated docs
added function for adding traits, updated examples and docs, added tests
released version 0.2
merged dev into master