Bubble and dew points with one or more components in the mixture at 0 composition #332

Due to numerical issues in the evaluation of the ideal gas contribution, bubble and dew point iterations currently fail if one of the mixture components has 0 composition. See #331 and #254

Re-initializing the eos without the zero component can be a solution, but might be inconvenient in some cases. For most situations in which this problem occurs, increasing the composition to a small positive value (e.g., 1e-20) can solve the issue without meaningful loss in accuracy.