Working version for iOS

[dariocavada]

• Correct stop monitoring: issue https://github.com/umair13adil/simple_beacons_flutter/issues/7
• Removed filtering by major and minor (It is better to have a common interface that works the same for ios and android): issue https://github.com/umair13adil/simple_beacons_flutter/issues/6
• Modified the example: issues https://github.com/umair13adil/simple_beacons_flutter/issues/8, https://github.com/umair13adil/simple_beacons_flutter/issues/3
• Modified the readme.MD file (remove of course the beacons_plugin dependecies to my fork)

This version should solve all the 4 issues in the list.

Thank you for this plugin.