Tau-leaping solver sensitive to parameter name case, consider making configuration case-insensitive.

[clorton]

Jaline et al. at Northwestern ran into an issue where following the documentation for configuring tau-leaping did not work. The documentation did not match the casing expected by the code. Initial fix is to update documentation. Better fix is to make the configuration case-insensitive. There is, for example, no need to differentiate between "Epsilon" and "epsilon" or "SSAruns" and "ssaruns".