DELIVER-2153: Add caption labels to dash manifests (#95)

* Add Label Attribute to Dash structure

* Add Labels on Dash manifest

* Updated tests to meet new label criteria

* Updated comments with a more accurate description of the subtitle functions

Co-authored-by: Jorge Guerra <jguerra@brightcocove.com>

add attrPublishTime, as publishTime must be present for @type='dynami…

…c' (#84)

Co-authored-by: liuyanhit <liuuyan@qiniu.com>

Release v3.0.1 with fix to go.mod for /v3 module path

Add go.mod file (#57)

Merge pull request #42 from zencoder/add-attributes

First stage adding additional parameters to match spec

Removed 'suite' and moved to using 'require' instead of 'assert' (#43)