Add support to choose changelog "style"

[engfragui]

I've started using this bitbucket-changelog for one of my project. I was wondering if you were thinking about somehow adding support for users to choose a changelog "style" that is different from the default one.

Default:

## 1.0.0
Feb 28th 18

- [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>

Maybe the user wants something like:

# 1.0.0 (2018-02-22)

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

I'm still not sure how the user will provide these inputs, for now I'm just curious to understand if this is something on your mind or something that you'll never want to support. Thanks

[mikestead]

@engfragui That's certainly something I'd be open to. Perhaps a theme option could be passed.

It's unfortunately not something I'd be looking at any time soon but would be open to PR's.

[kcabreradev]

@mikestead Are you still open to receive PR's for this feature? I'm interested on this