Merge pull request #13 from ruslanskorb/develop

Version bump (0.3.1)
Merge pull request #14 from ruslanskorb/develop

Version bump (0.4.0)
Merge pull request #15 from ruslanskorb/develop

[Fix] Code sample in the README.
Merge pull request #22 from ruslanskorb/develop

Version bump (0.5.0)
Not default FirstWeekDay fix;
Relocate util method;
Merge pull request #28 from alexeyhippie/FirstWeekday

First weekday