Fix Feedly CSS Changes

• Fix an issue caused by changes in the CSS styles in Feedly (#53)

Update URL of Mercury API

• Mercury API is now running on dedicated AWS instance
• Subscription to Mercury and API Key are no longer required

Remove support for Readability

• Mercury is now the recommended API

Add warning message for Readability users

• Help users with the migration to the new Mercury API

Fix new Feedly rendering

Thanks to @churchs19 and @patou for the pull requests

Add support for Mercury API

• Add support for the new Mercury parser API that will replace Readability in the future
• Fix the position of the images in some articles and shows them always at 100% of the width

Thanks a lot to @churchs19 for these contributions 👍

Improve management 3rd party library

Internal changes only.

Thanks @churchs19 !!

Add French and Spanish translations

• Add French and Spanish translations
• Add translation of the options page
• Add translation of the buttons to show the full article

Many thanks to @patou and @patou for the great support!!

Fix style of the button

• The button of FullyFeedly now matches the new style of the page

Fixed issue where Feedly changed class name for "Open Website" button

• Fixed issue where Feedly changed class name for "Open Website" button

Big thanks to @churchs19 for the pull request 👍