Allow brightcove.css styles for VideoJS player v6 to apply universally, size styling fixes for BCove

Change description

The many styles that were made to accommodate changes between Video.js players in v5 series and v6 were done using a .vjs-v6 selector. Remove those so the same styles can apply to subsequent versions. They work well with version 7, which is the major version in use by Brightcove.

https://appsembler.atlassian.net/browse/BLACK-1125

Fixes #27

Rebase off of master once #35 is merged

Type of change

[ ] Bug fix (fixes an issue)
[x] New feature (adds functionality)

Checklists

Development

[ ] Lint rules pass locally
[x] Application changes have been tested thoroughly
[ ] Automated tests covering modified code pass

Security

[x] Security impact of change has been considered
[ ] Code follows company security practices and guidelines

Code review

[x] Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
[ ] "Ready for review" label attached and reviewers assigned
[ ] Changes have been reviewed by at least one other contributor
[x] Pull request linked to task tracker where applicable

appsembler / xblock-video

Allow brightcove.css styles for VideoJS player v6 to apply universally, size styling fixes for BCove #36