* add some tests with default capture on the two parameter template and some notes about it in the README.md
remove the test from visual studio 2015
vs2015 doesn't seem to properly deal with is_assignable in the cases we care about so make a standalone version that is more direct in what we are doing
add version to appveyor and add some notes to the readme
fix a few test cases to make sure code is covered and test a few other paths
remove unneeded enum streaming operator
add some diagnostic escapes around trait code to eliminate gcc Wnarrowing warnings
work specification of the template operations
remove optional add some templates for options conversions
add the two parameter template for add_option
* Fix some comments from Code review and add more description
* fix case when string_view doesn't work to append to a string.
* This PR also addressed #300
* modify lexical_cast to take const std::string &, instead of by value to allow string_view in a few cases
* some tweaks with optional
* remove set_results function that was bypassing some of the result processing in some cases of config files.
* add positional Validator example and tests add CLI::Number validator.
* add positional Validator example and tests add CLI::Number validator.
* do some reformatting for style checks and remove auto in test lambda.
