Update Zencoder Gem

Version 2.4 of the Zencoder gem contained expiring SSL certificates
bundled inside the gem. 2.5 relies on system installed certificates.
Merge pull request #70 from tf/zencoder-ssl-fix

Update Zencoder Gem
Update CHANGELOG.md

Link to Pull request.
Makes Zencoder path configurable.

It's now possible to configure the destination path of files
processed by zencoder in the pageflow initializer.
Merge the path as the key `:path` into `zencoder_options`, for example:

    config.zencoder_options.merge!(
        [other options]
        :path => "/:zencoder_asset_version/custom/part/:id_partition/:filename"
    )

Paperclip interpolations apply.
Database Seed DSL

Replace procedural `pageflow/seeds` file with `Pageflow::Seeds` mixin
that provides a DSL to create seed records.
Fix audio player time display

fixes #17

Display short timestamps if duration is shorter than 10 minutes.
Merge pull request #74 from tf/audio-time-display

Fix audio player time display
Merge pull request #71 from kioopi/zencoder_path

Makes Zencoder path configurable.
Merge pull request #73 from tf/seeds

Database Seed DSL
Update CHANGELOG.md
ie9: fixes scrolling on background video page