Fix GitLab Smart links

Fixes an issues with GitLab Smart links #17

Support Smart Links

Added support for Smart Links.
Thanks @MPLinder !

Support Multiple {color} tags

Adds support for multiple {color} tags.
Thanks @swaters-atlassian!

Monospace: Support {}

Added support for curly brackets {} inside monospace JIRA tags.
Thanks @jervill !

Stricter unnamed link matching

The link regex as it existed could pick up some false positive links.
This code attempts to make the regex a bit more strict such that
the text inside square brackets must include at least 1 dot and
should not include any characters that are not allowed in URLs

Thanks @swaters-atlassian !

Bugfix: Multiple links

Added fix for multiple links on the same line.
Thanks @DanielHreben !

Bugfix: Regex loop for citations

Simplified the regex for converting citations as it was causing crashes for large citations.

Slack -> JIRA

Added Slack to Jira support

JIRA -> Slack Support

Initial support for converting JIRA to Slack