Add support for the prices API

[yES]

• I took the changes from the pull request Add support for the prices API. #246
• Addressed the comments that were raised there
• Added support for listing Prices using filters

[feliixx]

Thanks for taking over the PR @yES,

I took a quick look to your PR but there are several issues with it:

• the tests aren't succeeding -> please make sure that they pass locally. You can run them by launching a localStripe server and running ./test.sh
• please make sure that flake8 . doesn't return any error
• your IDE seems to have reformatted a bunch of files -> please remove all formatting related changes, as these changes are unrelated to the current PR and makes the overall diff harder to read

Can you please fix these, and then I'll take a more thorough look at this !

[yES]

@feliixx thanks for comments! I fixed issues and now CI should works correctly

[yES]

@feliixx could you review PR again please?

[adrienverge]

@yES, looking at the current pull request, it looks like you did not address multiple of @feliixx's comments. Can you check?

Keep in mind maintainers have limited time. Please make the PR perfect before asking any new review. I recommend looking at previous commits and other classes to see the coding style and what is expect.

[yES]

I rechecked code and fixed all issues