Ansible functions

This needs thorough testing, but I think it solves #2.  The first commit reorganizes parts of the jinja syntax file, but should have no effect at all on the highlighting.  The second commit uses the syntax cluster defined in the first commit to get the desired effect, highlighting "foo bar" in `when: foo bar` the same way it is highlighted in `"yaml string {{ foo bar }}"`.

Note that #26 currently breaks some test cases, so that should probably be resolved before this is considered.