Add parsers to search path

[trishnaguha]

Ref: #54

Feature request:
The search path to include the parsers directory adjacent to the playbook directory
It would be preferable to use the parser file name and default to parser_templates/{{ ansible_network_os }}/file.[yml|yaml]

[privateip]

Just to be explicit here, the default search path should be:

- {{ playbook_dir }/parser_templates/{{ ansible_network_os }}
- {{ playbook_dir }}/parser_templates
- {{ playbook_dir }}

with file extensions of *.yaml, *.yml, and *.json

/cc @jmcgill298