enhancement to `:as-is?` for specific value conversions

[codeperfector]

:as-is? was introduced in a previous issue as a solution to handle situations where number conversion is attempted if a value is a date or an ip address. #27
But I think it is still useful to preserve the normal parsing behavior of cprop for all other values in my env or property edn files.
I proposed a way to allow this using :as-is-paths which is a set of paths that can be provided for which if the property keys match, then no value conversion is done. All other values are parsed in the normal manner.
See PR #40

[tolitius]

I took some time to sleep on it, since new flags tend to pile up and complect things
but I do agree this is a needed functionality
thank you for your contribution, I left some comments on the pull request

[codeperfector]

Thanks for looking at my PR. I updated the branch with an additional commit for the changes you requested.