test that the emissions factors are retrieved for the correct year.

[sichen1234]

Add test that the emissions factors are retrieved for the correct year.

First complete #189

Then add test to verify that emissions in 2018 and 2019 are calculated with different emissions factors for the same utility and kwH of usage.

[sichen1234]

What we need here is a test to also verify that the amount of emissions calculated is correct. Pls take a look at the ST19 emissions factor of state CA. It should be different than the ST18 emissions factor. So for the same energy usage, ie 100 KWH, there should be different emissions calculated in 2018 and 2019.