Updated VDOT Calculator

I’ve made a number of changes to my VDOT calculator.

• The value of VDOT and VO2max are no longer assumed to be the same. The VDOT value is now a table lookup using the values given in Jack Daniels Running Formula, where VO2max remains a calculation. The values of VDOT and VO2max tend to be close when a longer race is given as input, but differ more for shorter distances.
• The Jack Daniels training paces use the VDOT values, but the predicted race performances and the FIRST training paces continue to use VO2max. I may change this prediction to use other formulas in the near future.
• I’ve added a pace for 800 meter aerobic intervals, based on linear interpolation of the faster and slower paces, as the book does not specify this distance.
• The error handling is improved, detecting more erroneous conditions.
• I’ve made it clearer that only the long runs are given for the Jack Daniels marathon plans, not the second quality workout. I’m not trying to replace the book, just make it easier to use.
• All instances of ‘VO2max’ should now be written correctly; there is a dot above the V and the 2 is subscript.