Merge pull request #170 from akashskypatel/master

Fix reference leaks #127 and #153

Merge branch 'master' of github.com:abner/flutter_js

added more information about testing on windows and linux

updated CHANGELOG.md

removed plugin_platform_interface dependency

Merge branch 'nullsafety' of github.com:abner/flutter_js into nullsafety

upgraded dependencies to better support to flutter 2

updated flutter project