Clone an stobject

[kylebaron]

• This is the pipeable table construction object
• It is an evironment, so special care when making copies

[kyleam]

Side remark: when running the tests, some deprecation warnings popped up. The tidyselect ones are resolved by gh-303.

[kylebaron]

Side remark: when running the tests, some deprecation warnings popped up.

Thanks. I totally missed #303 when you submitted it.

Will do comprehensive assessment of the tidyselect stuff once this string of PRs are through.