FEATURES:
  - `Add-JiraIssueAttachment`: Add an attachment to an issue (#137, [@beaudryj][])
  - `Get-JiraIssueAttachment`: Get attachments from issues (#137, [@beaudryj][])
  - `Remove-JiraIssueAttachment`: Remove attachments from issues (#137, [@beaudryj][])

IMPROVEMENTS:
  - `JiraPS.Issue` now has a property for Attachments `JiraPS.Attachment` (#137, [@beaudryj][])