Fixed issue #24 Move mailServerName to Web.config
Fixed issue #27 Scroll calendar vertically by mouse wheel when moving mouse over scrollbar
Update CONTRIBUTING.md

+Issue is closed after pull request number is specified
Merge pull request #26 from Bohdan-Tereta/master

Fixed issues #23, #24, #27
Merge pull request #31 from AnnaStorozhenko/master

Solved #18: ExportAbsenceToExel() and AbsenceControllerTests modified