List any phylogenetic reference(s) on calibration page.

Addresses #49.
Adding jump to manual instructions for NCBI updates.
Adding tools and instructions (in progress) for NCBI updates.
Tweaking link to NCBI-update tools and README
Progress on README
Cleanup markdown, tweak section titles
More work on README
Complete README for NCBI updates.

Addresses #14, with a manual solution for now.