preselections metadata (#59)

* Bump package version to 0.3.10

* Add meta box

Add a skeleton implementation of 'meta'. This makes the read/write
 editlist.mp4 test fail. This is because The meta subboxes are not yet
 implemented. When neither reader nor writer for meta were implemented,
 the test for reading/writing editlist.mp4 worked, but as soon as meta
 is added as a reader, the subboxes have to be implemented too to not
 fail this test.
 Rather than adding the additional boxes, we remove 'meta' from
 editlist.mp4.

* Add grpl box

* Add utf8string datatype

* Add prsl box

* Add the prsl box, unit tests, and an mp4 file for testing

* Implement FDIS version of prsl

* Make the interleaving tag is optional and contingent on a flag
* Use new test content

* Add labl box

* Implement FDIS version of labl

* read is_group_label from the flags instead of as a separate field
* represent is_group_label as boolean

* Add 'elng' box

* Add 'ardi' box

* Add 'kind' box

* Add 'imda' box

* Update bundles

Merge pull request #54 from Dash-Industry-Forum/feature/sttg

Add sttg box for WebVTT cue settings

Build package 0.3.7

Build for release 0.3.6

Merge pull request #34 from Orange-OpenSource/ImproveEfficiency

Improve writing process

Version bump

Update package.json

Bumped version, updated changelog

Updated package to 0.3.1