Check spelling in UPPER_CASE_SEPARATED_BY_UNDERSCORE

[antoniodgonzalez]

When using this plugin in my project, I found that upper case identifiers are not being spell checked. I'm using Redux in my project, and here it is a convention to name the actions with upper case, separated by underscore, like:

const MY_ACTION = "MY_ACTION";

I modified the checkSpelling function with a previous transformation to find tokens of the kind UPPER_CASE_SEPARATED_BY_UNDERSCORE and convert to something like upper case separated by underscore, so the next step will be able to check these words. I added a few tests for these cases.

Additionally, I added a test script to the package.json file to ease the test execution.

[aotaduy]

Thanks for the PR, I think I'll add a configuration option for this kind of strings, since they ussually are constants, and might get funky names on propose.

[aotaduy]

Could you please add a config option?

[aotaduy]

Made some changes recently that wouldn't allow merge. Could you please update. If not i will try to integrate your changes.

Thanks for the PR!