Modernize insert_by_period materialization

The [insert_by_period](https://github.com/fishtown-analytics/dbt-utils/blob/master/macros/materializations/insert_by_period_materialization.sql) materialization was written ~2 years ago, and since then, we've improved the way we write materializations. e.g.:
* Better API for relations (or maybe I just didn't use them correctly)
* No `non_destructive` flag
* Helpful functions like `make_temp_relation`

Additionally, this materialization doesn't work on warehouses other than Redshift (see dbt-labs/dbt-utils#189)

It's time to give this some love: check out the refreshed code for the [incremental](https://github.com/fishtown-analytics/dbt/blob/dev/barbara-gittings/core/dbt/include/global_project/macros/materializations/incremental/incremental.sql) materialization as a good starting point.