Initial merge: Dash sequence viewer

[shammamah-zz]

Dash Bio pull request

• This is a new component
• I am adding a feature to an existing component

Name and description of your component

Dash Bio component that can display a sequence of amino acids, with events like mouse selection, tooltips, and click events associated with a coverage (defined by the user). I also included a folder helpers that parses .fasta files (the most common file type I've found for amino acid sequences).

Main libraries used in component

• Make sure you add links!

Before asking for a review

• I have gone through the code review checklist

PR merging checklist

Please make sure you have done these things before asking for approval to finally merge.

• Replace usage.py by app_[app name].py and put that file into the tests/dash folder.
• Add your sample test data into the tests/sample_data folder. You should not need to add any files at the root level of the repository.
• Address all comments in the code review.
• Make sure you are up-to-date with the latest master: checkout the master branch with git checkout master, pull from latest master git pull, checkout to your branch git checkout your-branch, merge master into your branch git merge master. Resolve conflicts.
• Test all existing apps and make sure they are not broken and make changes as necessary to make it work with the other apps.
• Ensure that your requirements.txt is complete and contains the specific versions of all Python packages you are using (if you are running in a virtual environment and have only the necessary packages installed for your component, you can just use pip freeze > requirements.txt)
• Run your application successfully in a virtual environment
• Update/regenerate package-lock.json (run npm install)
• Regenerate tarball (run python setup.py sdist, then copy dist/dash_bio-0.0.1.tar.gz into the top-level directory)
• Ask for a final review and look for a 💃!

[shammamah-zz]

@VeraZab @wilzbach I made the changes you requested, please let me know if there is anything else!