Variadic parameters are unwieldly in this context

[Henry Sarabia]

Although variadic parameters seemed like a good idea at the time of creating the package, they actually lead to extra boilerplate when calling the package functions. The sliceconv package is meant for converting slices of primitive types to another slice of a primitive type; the use-case of converting a single variable is already covered under the regular strconv package and is out of scope for this package.

Package functions should simply take a slice of primitive types.