Refactoring TableFooter

[wdh2100]

Refactor from class component to functional component

ref : #1346

Sorry. When I split it in PR, it's lot..

codeSandBox : http://codesandbox.io/s/github/wdh2100/mui-datatables/tree/functional/tableFooter

[coveralls]

Coverage increased (+0.1%) to 73.112% when pulling 61fa2f0 on wdh2100:functional/tableFooter into 6891ed2 on gregnb:v3_1_0.

[wdh2100]

unnecessary codes

[patorjk]

@wdh2100 Can you verify that you ran "npm run test"? I had some issues but realized it they were already in the v3.1.0 branch (so not related to you). It's kind of late, so I'm thinking of saving the rest of these for next week's release. However, looks like I can't test from codesandbox so figured I'd ask before doing the merge.

[wdh2100]

What is the problem?
When I run 'npm run test' it works fine

[wdh2100]

but mocha.opts <--- deprecated

ref : https://github.com/mochajs/mocha/releases/tag/v8.0.0

[wdh2100]

Rebase v3.2.0

[patorjk]

Thank you for adding the tests. I have a footer feature I want to add for version 3.2.0. I'm going to merge this branch into the jumpToPage branch and work on it there.

[wdh2100]

@patorjk

thanks!