Start working on crawler

In order to send pull request
Add missing docs

As Minhee mentioned.
Make Crawler class and basic methods
Modify auto_discovery method to suit test.
Change string's double quote to single quote.
Add class attributes and methods.

__init__(), get_document_type, reset method. And methods normally return to
set class attributes.
Start working on crawler

In order to send pull request
Add missing docs

As Minhee mentioned.
Make Crawler class and basic methods
Modify auto_discovery method to suit test.
Change string's double quote to single quote.
Start working on crawler

In order to send pull request
Make Crawler class and basic methods
Modify auto_discovery method to suit test.
Change string's double quote to single quote.
Add class attributes and methods.

__init__(), get_document_type, reset method. And methods normally return to
set class attributes.
Disassemble class into functions.

In addition, add crawler test and modify auto_discovery function
Make parser.py and parser_test.py.
Parsing required tags in Feed Document.
Remove unused Errors.