Configurable global hostname setting.
Update changelog and documentation.
Remove prefix_ts config option

When I copied the example verbatim heka failed to load the plugin.
Fix typo

Who wants to restart heka if they don't need to :P
Missing type
Remove test config plugins that write to base_dir, and make sure
kafka plugins use Heka's configured hostname.
Merge pull request #1182 from mozilla-services/hostname_config_setting

Hostname config setting
Merge pull request #1184 from hydrajump/fix-docs

Fix docs
Improve sandbox inject_* error messages issue #1156
Merge pull request #1188 from mozilla-services/issue_1156

Improve sandbox inject_* error messages issue #1156