Merge branch 'hotfix/0.2.2'
Merge branch 'release/0.3'
Merge branch 'release/0.3.1'
Merge branch 'release/0.4'
Merge branch 'release/0.5'
Use a filelock to prevent running flush_queue concurrently
Add lockfile to the test pip files
Merge branch 'develop' into feature/filelock
Make the lock acquisition a decorator
Merge branch 'feature/filelock' into develop
Use a filelock to ensure that only a single instance of flush_queue can run at any time.

# Please enter a commit message to explain why this merge is necessary,
# especially if it merges an updated upstream into a topic branch.
#
# Lines starting with '#' will be ignored, and an empty message aborts
# the commit.
Bumped version number.
Merge branch 'release/0.5.1' into develop