Black theme

[toboil-features]

Wanna to enjoy OLED beauty of black levels, but app currently has only dark theme.

[billthefarmer]

You can have any theme you like for the formatted view using styles, see #61, #60, README.

[toboil-features]

On one hand, black theme works through css for "Read" mode, on the other hand, It now ignores Android preferences.
Also it does not changes theme for "Edit" mode.

As a reference, that's how F-Droid implemented it.