Update vdW radii to CRC handbook values

[rkingsbury]

Summary

This PR updates the van_der_waals_radius data used by the Element class from Wikipedia data to the latest values in the in the CRC Handbook of Chemistry and Physics. Important changes from the previous values include:

• Revised the value for H down by 0.1 angstrom as recommended in a critical review by Rowland and Taylor
• Added values for many lanthanides, actinides, and transition metals that were previously absent
• Updated values or many transition metals

All data, and the justification for which values were chosen, can be found in

"Atomic Radii of the Elements" in CRC Handbook of Chemistry and Physics, 91st Ed.; Haynes, W.M., Ed.; CRC Press: Boca Raton, FL, 2010.

[rkingsbury]

Git does not seem well-equipped to diff .json files, so you can use this online tool to better see the changes:

https://jsoncompare.com/#!/diff/id=6924b719277a2a2b7a630352828d155c&fullscreen/

click the 'lint' button on both panes and you will see each change nicely highlighted

[coveralls]

Coverage decreased (-0.6%) to 83.007% when pulling 1c23fb5 on rkingsbury:vdw_data into ad5cb53 on materialsproject:master.

[mkhorton]

Thank you @rkingsbury , definitely happy to have data sourced from somewhere that isn't wikipedia here :-)