feat(config): Add support to ignore paths on per-rule basis

Example of configuration to use this feature:

    # For all rules
    ignore: |
      *.dont-lint-me.yaml
      /bin/
      !/bin/*.lint-me-anyway.yaml

    rules:
      key-duplicates:
        ignore: |
          generated
          *.template.yaml
      trailing-spaces:
        ignore: |
          *.ignore-trailing-spaces.yaml
          /ascii-art/*

Closes #43.

README.rst

@@ -119,6 +119,27 @@ or for a whole block:
    consectetur : adipiscing elit
  # yamllint enable
 
+Specific files can be ignored (totally or for some rules only) using a
+``.gitignore``-style pattern:
+
+.. code:: yaml
+
+ # For all rules
+ ignore: |
+   *.dont-lint-me.yaml
+   /bin/
+   !/bin/*.lint-me-anyway.yaml
+
+ rules:
+   key-duplicates:
+     ignore: |
+       generated
+       *.template.yaml
+   trailing-spaces:
+     ignore: |
+       *.ignore-trailing-spaces.yaml
+       /ascii-art/*
+
 `Read more in the complete documentation! <https://yamllint.readthedocs.io/>`_
 
 License