This #30 PR introduced code quality issues that should be fixed.

Most of them are in https://github.com/topcoder-platform/topcoder-react-lib/blob/1e4b154636c86c111b964c0258e6a6706735cf1a/src/services/challenges.js but everything should be checked and fixed.

• Fix eslint issues and revert rules to the default configs
• Fix many typos v3 => v4 in method documentation.
• We use the getApiResponsePayloadV3() method with the response from the V4.
• getApiV3 is defined but never used.
• We defined both this.private.api and this.private.apiV4 as getApiV4(tokenV3). This is confusing.