* Add autoprefixer to css build

* also use autoprefixer on theme files

* UI: Repo header tweaks

- Use basic buttons on the header buttons, matching gogs
- Make 'Manage topic' text smaller, remove margin-left with no topics
present
- Move various inline styles to CSS
- Use flexbox on header title and buttons

* fix indentation

* reverse media query wrapping

* fix inconsisten whitespace

* switch gitter to discord for drone.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* add event

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

* only notify build fail message.

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>

That is annoying on Windows, since the editor will change the file if
you just open it. Git will checking as LF anyway.

We are using gofmt to format our code. This will emit tabs.
The standard is tabs which is 8 spaces.

- Refactor code to use sync.UniqueQueue
- Closes #3509

[CI SKIP]