Firthlogist

Added
- `test_vars` option to specify the variable(s) for which to calculate PL confidence intervals and p-values.
Fixed
- Fixed bug where `.summary(xname)` would append `Intercept` to `xname` such that repeated calls would break.

Added
- Option to use Wald method for computing p-values and confidence intervals instead of LRT and profile likelihood. Set `wald=True` to use ([11](https://github.com/jzluo/firthlogist/pull/11)).
- Tests for `load_sex2()` and `load_endometrial()` ([9](https://github.com/jzluo/firthlogist/pull/9)).
- Test for profile likelihood confidence intervals ([9](https://github.com/jzluo/firthlogist/pull/9)).
Changed
- `skip_lrt` option is now `skip_pvals` ([11](https://github.com/jzluo/firthlogist/pull/11)).
Fixed
- `.summary()` no longer breaks if skipping confidence interval or p-value calculation ([11](https://github.com/jzluo/firthlogist/pull/11)).
Removed
- Diabetes and sex2 csv files removed from testing dir ([9](https://github.com/jzluo/firthlogist/pull/9)).

Added
- Added the endometrial cancer dataset analyzed in Heinze and Schemper, 2002. Load using `load_endometrial()` ([8](https://github.com/jzluo/firthlogist/pull/8)).
Changed
- Disabled step-halving by default to follow `logistf`, which disabled it in version 1.24.1 for some reason ([8](https://github.com/jzluo/firthlogist/pull/8)).

v0.3.0 adds a couple of convenience features.
Added
- Added `.summary()` method to print summary of results ([6](https://github.com/jzluo/firthlogist/pull/6)). See the readme for a usage example.
- Added the sex2 dataset from logistf as `load_sex2()` ([7](https://github.com/jzluo/firthlogist/pull/7)).

v0.2.0 is the MVP release implemented in Numpy and Scipy.
Added
- Calculate confidence intervals using profile penalized likelihood ([5](https://github.com/jzluo/firthlogist/pull/5)).
- `skip_ci` parameter to skip calculation of confidence intervals.
- `alpha` parameter to specify confidence interval.
- `pl_max_iter`, `pl_max_halfstep`, `pl_max_stepsize` parameters for controlling profile penalized likelihood procedure.
Changed
- Predictions calculated during fitting procedure are now clipped to the range `[1e-15, 1-1e-15]` instead of `[0, 1]`.

Fixed
- Added missing `loglik_` attribute to readme.