Replace chai.should with chai.expect

[yopereir]

Fixes #1687

Converted all cases of .should to expect and added 'const { expect } = require('chai');' to relevant files.
Did not touch any other files except the test files.

[nventuro]

Woot, thank you very much for this @RCYP! Note that there are multiple tests failing due to usage of exxpect instead of expect.

[stale]

Hi all!
This Pull Request has not had any recent activity, is it still relevant? If so, what is blocking it? Is there anything we can do to help move it forward?
Thanks!

[nventuro]

Note that @alanarvelo is working on a very similar thing at #1804

[yopereir]

idk why the build is failing.. i've checked out from the latest master branch and put the test cases but it still fails.. seems @alanarvelo has got it so you can use his instead.

[alanarvelo]

Hi @RCYP sorry to have jumped in, I thought you had paused your effort.
In the Details section provided by Travis CI it says the unit tests and linting tests are failing.

You can prevent this from happening by running those tests in your local environment by typing truffle test file/you/changed and npm lint respectively, every time you make changes to a file.

[yopereir]

the coverage check is failing at Address.sol for some reason.. i'm using the same file from the master. any idea what the issue might be?

[frangio]

Lovely! Thank you @RCYP!