Document and fix the bug

This week, I wrote the document and fix the bug.

Details at

Download only what is new

https://bitbucket.org/BMI/medicurator/issues/6/download-only-what-is-new-when-attempting


The document:

https://bitbucket.org/BMI/medicurator/issues/5/medicurator-readthedocs-documentation

Fix the hard code the API_key

https://bitbucket.org/BMI/medicurator/issues/7/avoid-the-need-to-hard-code-the-api-key