Update Changelog & Podspec for 1.7.0

fix: use proper calendar to calculate next month for weekview (#551)

Add license and pod badge to README

Merge pull request #480 from CVCalendar/swift4

Swift4

Update docs for 1.5.2

Update docs for 1.5.1

Fix #188

Merge pull request #387 from beset/master

When the newly set presentedDate equals to the old presentedDate, presentedDate don’t update

Update to Swift 3 Syntax, remove CVDate-typealias, remove warnings"

Merge pull request #346 from nikolay-dementiev/feature

Nil-Safety for #337, thanks @nikolay-dementiev