Retrieve Jira issues from commit messages

[engfragui]

bitbucket-changelog is able to associate Jira issues with each pull request.

- [1](https://link-to-pull-request) Pull Request title <small>[Author name](https://link-to-developer-profile) ([issue-number](https://link-to-jira-issue)) - 28/2/18</small>

The Jira issues are retrieved from:

• title of the pull request
• description of the pull request
• branch name

However, it would be useful if the Jira issues were also retrieved based on the commit messages that belong to that Pull Request since this is how many developers "attach" tickets to their bitbucket Pull Requests.