Initial supporting for defining non-standard input units

An additional parameter "input_units" was added where a user can specify the unit types of the inputs.

Initial attempt at Daily and Hourly classes (instead of functions)

Implemented Daily/Hourly classes similar to RefET-GEE

Instead of setting the "surface" parameter, the user calls the ".etr()"
or ".eto()" method on the build Daily or Hourly class.

Made "asce" method the default for all functions and calculations

v0.2.4

Switching calculation default method to asce (from refet)

Additional "ASCE" vs "RefET" modifications

Summary of changes from 0.2:
Default rso_type to 'simple' when method == 'asce' and to 'full' when method == 'refet'.
Separate asce/refet calculations for Es slope.
Set vapor pressure deficits less than 0 to 0.

New "surface" and "method" parameters

These new parameters replace the "refet_type" and "asce_flag" parameters.

Initial Release

v0.1.0

Removing code coverage