v0.2.5

• Fix bug where exog and group_by did not handle str inputs e.g. exog="x".
• Fix bug where group_by for method='fwl' with exactly 1 exog variable did not work. (Explanation: method='fwl' dispatches to a different macro for the special case of 1 exog variable, and group_by was not implemented correctly here.)
• Fix bug where safe mode did not work for method='chol'
• Improved docs by hiding everything except ols(), improved description of ols() macro, and added missing arg.