ChemSpiPy v2.0.0

Implemented enhancements:

• Access "data source" information through ChemSpider #3
• Switch to new RSC REST API #12 (mcs07)

Fixed bugs:

• Authentication problem #11

Closed issues:

• Make conda-forge recipe #13
• return # of data sources in search results #10

Merged pull requests:

• Update docs for new RSC REST API #14 (mcs07)