Do some complex processing to catch stale element errors from selenium with caching.
Wrap calls to click and set to check for stale element errors.
Provide more information when a setting cannot be located, and support default configuration values.
In error message from config_get, print the correct YAML config file.
Element procedures can now take arguments.
Add procedures that take arguments to the search page for testing.
Check whether an element responds to :present?, as collections of elements don't.
Allow elements to be evaluated under different parents.

The following option behaviour is now supported, where element1 and element2
are both gless elements: "element1.element2", which refers to element2
evaluated when element1 is considered the parent element.
Remove duplicate "Object level" header in documentation.
Support more types of parents.
In find_elem, tries += 1 was incorrectly placed, causing an infinite loop.
Add support for restricting element selection by children.
In test_github example, test :child selectors.
Check whether elements restricted by children are arrays, and avoid returning an element without non-watir selectors when it cannot be found with them.
Child elements can take arguments.
Better handling of child selectors without arguments.
Add documentation to :proc, and pass the page object.
Update :proc in test_github for compatibility with previous commit.

Note that this series of commits as a whole does not break backwards
compatibility, since multiple arguments were previously not supported.
Rename gless's parent to avoid ambiguity with the underlying watir element's parent.
Rename missing parent attribute to gless_parent.