Major update due to NIH-OPA's iCite data change

Updates to accommodate the NIH-OPA's changes in their iCite data and API:

Update for NIH-OCC field, authors, now possibly not existing by @dvklopfenstein in #86:

1. Update for new NIH-OCC data format where some fields may no longer exist such as: authors nih_percentile pmid
2. NIH-OCC documentation lowered max PMIDs to 200 -> updated code to accommodate this NIH change.
3. Improved reporting for PMIDs not found in NIH-OCC database
4. Fixes #87

Additional updates in this release:

• Simplify TOC by @dvklopfenstein in #82
• Separate install & setup by @dvklopfenstein in #83
• Add graphic to notes by @dvklopfenstein in #84
• Add bioconda and anaconda badges by @dvklopfenstein in #85

Full Changelog: v0.2.0...v0.3.0