Bump version to 1.5.1

Merge pull request button#136 from button/wes/introduce_swiftier_regi…

…stration

A more Swift friendly route registration

bump to version 1.4.0

bump to 1.3.0

Update to 1.2.2

Update to 1.2.1

Release 1.2.0

Merge pull request button#59 from usebutton/feature/universal_link_su…

…pport

Adds support for universal links

Merge pull request button#50 from usebutton/chris/deep_link_kit

DeepLink SDK is now DeepLinkKit

Merge pull request button#51 from usebutton/chris/deprecate_deeplinksdk

Deprecate DeepLinkSDK