Fix error check string to fix #25

[afrase]

Description

• Removed the double quote from the body check since it appears a space is added after the colon.
• Added CHANGELOG.md file.

Related Issue

25

Motivation and Context

An error wasn't being raised when the number of credits on the account was zero.

Checklist:

• [x] My code follows the code style of this project.
• [x] I have added tests to cover my changes.
• [x] All new and existing tests passed.

[codeclimate[bot]]

Code Climate has analyzed commit 1091bc03 and detected 0 issues on this pull request.

The test coverage on the diff in this pull request is 100.0% (50% is the threshold).

This pull request will bring the total coverage in the repository to 94.8% (0.0% change).

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