Release version 0.4.0

This release adds support for pulling statistics from TCP sockets, which allows users to pull statistics from remote HAProxy servers. There are some minor changes in the code in terms of readability and PEP257 compatible docstrings. We also fix a crash when we process statistics from HAProxy version 1.5 as "CurrSslConns" metric doesn't exist in that version. Last but not least, this release adds support for pulling few more statistics (see 4608202).

Changelog:

• RELEASE 0.4.0 version
• Handle the absent of daemon's metric
• It's a counter, so should be in different section
• Update the list of supported metrics
• Use int rather string in the default values
• Use int rather string in default value
• Switch to correct section name for pycodestyle
• PEP257 compatible docstrings
• Switch from yarl.UR to urlparse from standard Python library
• Update reference of UNIX sockets to include TCP
• PEP257 compatible docstring
• Simplify the return logic of two functions
• Add configuration_check_for_servers()
• PEP257 compatible docstrings
• Disable pylint warning for too-many-branches
• Change the log severity to info for task report
• Add support for pulling statistics from TCP sockets
• Make that code more readable
• PEP257 compatible docstrinigs
• Fix typo in README