Update package documentation to proper CVrisk-package sentinel file.

Improve risk score calculation performance for large datasets. Contribution by @hhubbell

Add other race in ACC/AHA 2013 ASCVD risk score. Other race have same risk as White race as used in the official online calculator. See #2.

Added two additional risk scores: - MESA 2015 10-year ASCVD risk (traditional risk factors) - MESA 2015 10-year ASCVD risk (using coronary artery calcium)

Out of range or missing inputs now return NA instead of erroring out

Initial CRAN release.