Testrail-api

* Fix get_users

* Added github actions
* Removed `.travis.yml`
* Update dev requirements
* Updated endpoints:
* get_attachments_for_case
* get_attachments_for_plan
* get_attachments_for_run
* get_history_for_case
* add_case_field
* get_milestones
* get_projects
* get_results
* get_results_for_case
* get_results_for_run
* get_sections
* get_tests
* Updated type annotations and docstrings:
* get_attachment
* delete_attachment
* get_cases
* get_plans
* get_reports
* get_current_user

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