Add CDNJS version badge in readme

[kennynaoh]

This will add the badge to show its version on CDNJS and also link to its page on CDNJS!

[wjcrowcroft]

@kennynaoh Thanks for this pull request. Mind submitting it on the openexchangerates/accounting.js repository?

[kennynaoh]

Hello @wjcrowcroft We add this library https://cdnjs.com/libraries/accounting.js on CDNJS already, but not this https://github.com/openexchangerates/accounting.js, so I can't submit the badge on it.

[wjcrowcroft]

@kennynaoh I see - https://github.com/openexchangerates/accounting.js is the official repository for the library, and this fork may not be maintained alongside it. Are you able to update the library on cdnjs.com to the correct base repository?

[wjcrowcroft]

@kennynaoh Also, the cdnjs.com page for accounting.js should be updated to use the correct homepage URL:

http://openexchangerates.github.io/accounting.js/

The previous URL doesn't exist any more and doesn't forward either.

(If this isn't something you're responsible for, could you please point us in the right direction for getting these updated? Thanks.)

[kennynaoh]

@wjcrowcroft So you want to update the git repo and the homepage on cdnjs? https://github.com/cdnjs/cdnjs/blob/master/ajax/libs/accounting.js/package.json#L26 BTW, whould you like to open an issue to fix the problems above on cdnjs? https://github.com/cdnjs/cdnjs/issues