Fixed the validation of the element in selectOption

Checkboxes are not allowed in this method.
Closes #135
Merge pull request #149 from stof/fix_type_check

Fixed the validation of the element in selectOption
Added executeJsOnElement to avoid duplicate XPath query when we have it
Switched the the native webdriver API to get the input type
Refactored the safeguard on input type

The method now reuses the webdriver element found to perform the action
instead of searching it by itself. The method is also more generic to
avoid duplication between code checking for file or checkbox inputs.