Remove lockfiles from some cron scripts

The scripts using the lockfile command have not yet hit production, and we need different syntax for Ubuntu.

This commit should not have side effects on our production servers, but I'm putting it in a pull request so people will be notified.
Use nice when calling rake task:task_name

This is brings the task.sh in line with the one currently used in production on
the congress-api box.
Symlink scripts in config/cron/scripts

Currently, the scripts on server are not necessarily those checked into this
repo. Now, any scripts checked into config/cron/scripts will be symlinked to
/projects/congress-api/congress/shared/cron.
Fix rake syntax in us-sync-upcoming-house-floor.sh

Should have task prefix.
Fix crontab symlink in fabfile.

Contents of this project's config/cron/scripts should be runnable from
congress/shared/cron

Evaluates to 'ln -sf
/projects/congress-api/congress/versions/TIMESTAMP/config/cron/scripts
/projects/congress-api/congress/shared/cron'
Merge pull request #476 from sunlightlabs/lockfiles

Use repo cron scripts on production server

@timball just took a look at this