Add Resolver.get() option to retrieve node with name "."

Hi @c0fec0de, I've run into a case where a user named a node "." and the Resolver fails to retrieve the node, instead returning its parent node. Here's a MWE: ``` from anytree import Node, Resolver # Create a tree structure root = Node("root") a1 = Node("a1", parent=root) dot = Node(".", parent=a1) # Create a resolver resolver = Resolver('name') # This finds the parent instead of the dot node print(resolver.get(root, "/root/a1/.")) ``` Would you be open to adding an option to the `Resolver.get()` method to disable pattern matching? I'm thinking something like: `resolver.get(root, "/root/a1/.", strict=True)` to disable pattern matching. Not married to the `strict` name, just using it as an example. The default kwarg value could be False to ensure backwards compatibility. If you'd be amenable to something like this, I could put together a PR. Alternatively, if there is a workaround for retrieving nodes in cases like this please let me know. I'd be open to using that method. Appreciate your time, Scott