* Slack Import unit tests (for some functions).
Covers the completely self contained functions in the Slack Importer
that are straightforward to unit test.
JSON processing functions are not yet unit tested.
* Unit tests for Slack Import JSON parsing.
This tests the 3 functions for parsing JSON, using a sample set of
Slack data for posts, channels, and users.
* PLT-3552 Partially-fixed an invalid test case
* PLT-3551 Removed an invalid test case
* PLT-3482 Added a test case for multiple lists separated by text
* PLT-3482 Updated marked to fix multiple lists separated by text
* Removed MattermostLexer since it was exactly the same as the default marked one
* Updated list autonumbering to always start numbering from the first item's number
* Updated twemoji to properly recognize Unicode 8.0 emojis
* Updated unicode emoji parser to only render emojis we support as images
* Corrected filename for South African flag emoji
* Added Mattermost emoticons!
* Added additional emoticons to test files
* Render attachment fields similar to Slack
* Add /loadtest json url command
This allows us to easily create test posts with
more props like Slack attachments
