v0.8.0

v0.8.0 separates date and time functionality into a temporal module. An auth MixIn class enables sharing of authentication between modules, an important step for cloud data access, and allows users to easily customize their auth settings (e.g. for proxies). Use of intake to read in data groups/variables was deprecated in favor of direct reads through Xarray. Clarifications to authorship, citation, and attribution are also included and support for ATL23 was added.