－Added EnsembleVotingRegressor in regressor folder
－also including my own test file in the test folder.

Hi professor,
I have move ensemble_vote_regressor into the right folder and also change the form of test file. However, I can't fully understand the working flow of the test file so I just imitate the test file for ensemble_voting_classifer.
I have also include my own test outputs which is using graph to compare the performance of EnsembleVoting, Stacking and Voting in Regressor.

It's my first time trying to tackle such problem. So I am willing to receive any kinds of advices and please feel free to correct any of my mistakes!