Add horizontal regridding

[tomvothecoder]

Blocked by #71

Describe the solution you'd like

Create time average of data with proper temporal weighting accounting for calendar peculiarities (e.g., from monthly mean, seasonal mean, or annual mean from monthly/sub-monthly data)

Acceptance criteria:

• Decide if we want to wrap third-party library calls into utility method(s), or have user rely on library APIs directly
• Ensure we can convert between 0:360 longitude and -180:180 longitude

Describe alternatives you've considered

• Does SciPy do this?
• Wrap xESMF/ESMF?
• Wrap TempestRemap?

Additional context

CDAT/CDMS uses SCRIP2, ESMF, and regrid2

Prototype:

• Regrid example