tranSurv 1.2.1

* Add optim() in search and update searching algorithm
* Fixed bugs in piecewise models

tranSurv 1.2.1

* Use grid search (rootSolve then optim) in finding a
* Updated piecewise model so `a` is optimized globally
* Added goodness of fit test

tranSurv 1.2.0

* Passed CRAN checks
* Added regression method, `trReg()`