chore(ionic): release beta.7

release: v1.3.1 "el salvador"

style(toast): fix linter error

chore(packaging): dependency version updates

Removed redundant this.nav declaration (ionic-team#6244)

`this.nav = nav` is already present due to the `public nav: NavController` declaration, having it in the constructor as well is redundant

chore(sass): fix Sass linter errors

chore(package): update README

chore(ionic): release beta 2 and update changelog

chore: release ionic beta.1

chore(): beta release 🎉