Remove usage of decrecated _ dplyr functions

`tbltools` makes liberal usage of functions in `dplyr` that are now depcrecated. E.g. `group_by_`, `select_`. If you pull up the help for these function the documentation says:

> dplyr used to offer twin versions of each verb suffixed with an underscore. These versions had standard evaluation (SE) semantics: rather than taking arguments by code, like NSE verbs, they took arguments by value. Their purpose was to make it possible to program with dplyr. However, dplyr now uses tidy evaluation semantics. NSE verbs still capture their arguments, but you can now unquote parts of these arguments. This offers full programmability with NSE verbs. Thus, the underscored versions are now superfluous.

> Unquoting triggers immediate evaluation of its operand and inlines the result within the captured expression. This result can be a value or an expression to be evaluated later with the rest of the argument. See vignette("programming") for more information.

Since this package is widely used in BAAQMD, it should probably not rely on functions that are now deprecated in other libraries.