Update Package.swift and Podspec for Xcode 12.5

Xcode 12.5 support

Update release to 3.1.8

Signed-off-by: Kemar White <gailsx@gmail.com>

Updated release to 3.1.7

Tagged for Swift package manager support.

Release 3.1.5

Signed-off-by: Kemar White <gailsx@gmail.com>

Release 3.1.5

Signed-off-by: Kemar White <gailsx@gmail.com>

Release 3.1.4

Update podspec to 3.1.3

Merge pull request PureLayout#222 from PureLayout/lwdupont-patch-1

Properly release the new version.