Docs: Add reference to pandaSDMX to the pandas Ecosystem page in the API section
I would be pleased if pandaSDMx (http://pandasdmx.readthedocs.org) could be added to the pandas Ecosystem directory. The following text is just a proposal, feel free to change it as you see fit:

"pandaSDMX is a libraryaimed at becoming the most intuitive and versatile tool to retrieve and acquire statistical data and metadata disseminated in 
SDMX
 format. As of v0.2 it works well with the SDMX services of the European statistics office (Eurostat) and the European Central Bank (ECB) both of which provide hundreds of thousands social and economic indicators. While pandaSDMX is extensible
to cater any output format, it currently exports SDMX datasets with observations and/or attributes to multi-indexed pandas DataFrames and Series. Metadata such as datastructure definitions, dataflow definitions, and code lists are represented in terms of the SDMX-2.1 information model."
