updating all metrics to float64 as per open-meteo/open-meteo#410

Release v0.1.2

* Fix: Options struct can now specify both daily and hourly metrics
* Included an example for daily metrics in the readme

v0.1.1 includes support for the newly released daily metrics at open-…

…meteo.com

Note: compared to v0.1.0, the format of the output has changed. It used to contain
a Metrics attribute containing a map[string]float64 with the hourly metrics. Because
open-meteo introduced daily metrics, these are now renamed to HourlyMetrics and
DailyMetrics.

Breaking backwards compatibility was a reasonable trade-off as the module was only
released 2 days ago.

cleanup for v0.1.0