Add missing methods to Series

[mrocklin]

Pandas methods like to_timestamp are trivial to add to dask.dataframe. We should go through the API and verify that we've implemented everything like this that is more-or-less trivial to do.

[postelrich]

This is the list I came up of missing methods that should be relatively simple to add.

• T
• align
• all
• any
• applymap
• axes
• combine
• combineAdd
• combineMult
• combine_first
• compound
• corrwith
• diff
• divide
• dot
• duplicated
• eq
• ewm
• expanding
• first_valid_index
• ge
• get_value
• gt
• iget_value
• irow
• isin
• items
• iteritems
• kurt -> manually calculate 4th moment?
• kurtosis ^^^
• last_valid_index
• le
• lt
• mad -> manually calculate?
• ne
• nsmallest
• prod
• product
• reindex
• reindex_axis
• round
• select_dtypes
• stack
• std -> manually calculate?
• to_string
• to_timestamp
• transpose
• unstack
• var -> manually calculate?

[mrocklin]

Nice list. It might be interesting to organize these methods by communication patterns that are already well supported with generic functions like elemwise (round, to_timestamp, to_string, ge, le, ...) and reduction (nsmallest, any, all, ...). There will also be others, like kurt, that will require more thought, and transpose, which we probably can't easily support.