If I understand what you're asking for, you want to be able to update your project, but still allow people to download this version. You want people to be able to download v1.1 while working on v1.2.
In version control this is usually done with a tag. A tag simply puts a label on a commit. It's kind of like a branch, but it never moves. Then people can checkout that tag. For example...
# This tags the current commit as v1.1
git tag v1.1
# This uploads your tags.
git push --tags
# Then anyone can checkout v1.1
git checkout v1.1
Using tags for releases allows anyone to easily checkout a release, and you can continue to commit small changes with good commit messages.
Here's Bitbucket's own documentation about tagging.
Other systems like Github go a step further and turn your tags into "releases" which are downloadable from their web site. Bitbucket does not appear to support this feature, but it seems it's in the works.
As for branching, if v1.1 is done then there's no need to branch for a new release. Continue working on master
and making new tags for new releases.
Where version branches are appropriate is for very large projects which have to maintain multiple major versions simultaneously. For example, a programming language might need to maintain v2 while working on v3 at the same time. So they might have a v2 branch and a v3 branch. Each would still have their own tags (v2.2.4, v3.0.3, etc...).