add possibility to fetch company information

* we can use `client.company.all` to fetch company information
* add possibility to pass token to `company_file` option
* refactor `model` method
* simplify models parent classes
Add possibility to work with invoices.
Mention invoice model in readme.
add deletion method
Merge pull request #7 from timsly/company-data

add possibility to fetch company information
bump version
Merge pull request #10 from edariedl/invoice-model

Add possibility to work with invoices.
bump version
add EmployeePayrollAdvice model
Merge pull request #12 from Thinkei/employee-payroll-advice

Add EmployeePayrollAdvice model
bump version
Merge pull request #11 from Thinkei/deletion

Add deletion method
bump version