Improvements

[feelgood-interface]

1. (Breaking change) Use consistent naming across the functions, save_path and hide_elements.
2. get_element: get location of element before scrolling, to avoid stale element exception..
3. get_element: delete the temporary full screenshot.
4. get_element: don't add ".png" to image_name, as the default value indicates that the name should include the extension.
5. (Breaking change) full_screenshot: use lower case function name
6. (Breaking change) full_screenshot: revert Fix: Fixed issue when taking screenshots and images are displayed cro… #18, which causes the problems in issue Full Screenshot function not taking images for a page bigger than the window #21. I have not come across the problem mentioned in Fix: Fixed issue when taking screenshots and images are displayed cro… #18.
7. full_screenshot: call hide_elements before getting the final page size
8. full_screenshot: call hide_elements on each rectangle. Currently the element is not hidden in the first iteration.
9. Add unit tests.
10. Fix documentation.
11. get_element: Scroll to top of page before getting location, to get absolute coordinates. This might not fix location for all cases.
12. hide_elements: use !important keyword to override any other display styles.

[sam4u3]

Will review this once we get free time from work.