Issue 19 - add n_iterations as a parameter in estimate_timecourse_params_tf()

[shackett]

Description of your changes

• Added an example dataset which was poorly fit by estimate_timecourse_params_tf().
  • added a test which verified that the logLik is calculated correctly. Its just super low because the optimizer is not given enough time to converge. Exposed # of iterations which along with learning rate can be used to provide room for convergence. With some minor tweaking the poorly fit curve is now fit perfectly with a modest likelihood. Closes Intercepts are not well fit if very far from zero #19

Issue ticket number and link

Type of change

• Bug fix
• New feature
  • Backwards Incompatible?
• Refactoring / code clean-up
• Documentation add / update
• Automated Test
• Other (please specify)

(If applicable) How has this been tested?