feat(firefox meta): auto-update

Add `updateURL` install manifest property, add `https` update manifest
link to `package.json` under `extensionUpdateUrls.firefox` key.

See https://developer.mozilla.org/en-US/Add-ons/Install_Manifests#updateURL
for more on `updateURL` and `updateKey`.

This commit targets #153.
style(build): rename to `maxthon-packer.exe`

Rename `maxthon-packager.exe` to `maxthon-packer.exe`.

This closes #133.
feat(settings): remove "Others" tab

Move everything from "Others" section to "Interface",
move "Reset Settings" and "View localStorage" buttons to "Backup".
Remove "Others" tab completely.

This closes #157.
feat(opera meta): auto-update

Add `update-description` element to `config.xml`, add `https` update
config link to `package.json` under `extensionUpdateUrls.opera` key.

This commit targets #153.
docs(README): add a link to site

- project is alpha
- go to site to install
- we support browsers: ...

This closes #154.
feat(settings): always show as popover

Always show settings as a popover, not as a separate page.
Also open it if url ends with `#<%= name %>`.

This closes #66.
feat(modal): add `modal` module, use for changelog

Add `modal` module for displaying vk wide style popups.
Use it for displaying changelog instead of custom hardcoded solution.

This is related to #156.