* add persistent option for modprobe
* add suggested changes + fix broken test
* change modprobe module path in tests due to rebase
* change persistent option type from bool to str with choices
* fix unused import
* add example with persistent option
* fix some minor issues after review
- move regexps compiling to __init__
- move AnsibleModule to build_module function and use this function in tests instead of AnsibleModule
- fix terminlogy issue in documentation
* fix unused-import
