Testrail-api

Added endpoints
* copy_cases_to_section
* move_cases_to_section
* move_section
* get_shared_step
* get_shared_steps
* add_shared_step
* update_shared_step
* delete_shared_step

Updated endpoints
* get_results
* get_results_for_case
* get_results_for_run
* get_runs
* close_run
* delete_run
* get_sections
* get_test
* get_tests
* get_users

* Added method add_attachment_to_case (thank samdaoust )
* Added tests
* Updating dependencies

Added methods:
* get_history_for_case
* update_cases
* get_current_user

Added soft parameter for methods:
* delete_case
* delete_cases
* delete_run
* delete_section
* delete_suite

Added and updated method descriptions
Updated dev dependencies

* Converting datetime object to UNIX timestamp

Updated endpoints:
* add_milestone
* get_users (thank Enacero )

Added endpoints:
* add_run_to_plan_entry
* update_run_in_plan_entry
* delete_run_from_plan_entry

* Casting a boolean to an integer for get requests