Uncaught TypeError: editor.getCommentStrings is not a function

# Steps to reproduce:

1. Select text.
2. Run the convert action.
3. Select a font.

The error is thrown immediately. I assume it's because APIs have changed in newer Atom versions.

**Atom**: 1.23.0-beta1 x64
**Electron**: 1.6.15
**OS**: Mac OS X 10.13.1
**Thrown From**: [figlet](https://github.com/abe33/atom-figlet) package 0.5.4

### Stack Trace

Uncaught TypeError: editor.getCommentStrings is not a function

```
At /Users/alexp/.atom/packages/figlet/lib/figlet.coffee:68

TypeError: editor.getCommentStrings is not a function
at Object.getTextToConvert (/packages/figlet/lib/figlet.coffee:68:117)
at Object.convert (/packages/figlet/lib/figlet.coffee:38:44)
at FigletFontView.module.exports.FigletFontView.confirmed (/packages/figlet/lib/figlet-font-view.coffee:62:20)
at FigletFontView.module.exports.SelectListView.confirmSelection (/packages/git-plus/node_modules/atom-space-pen-views/lib/select-list-view.js:338:21)
at /packages/git-plus/node_modules/atom-space-pen-views/lib/select-list-view.js:109:19)
at CommandRegistry.handleCommandEvent (/Applications/Atom Beta.app/Contents/Resources/app/src/command-registry.js:388:36)
at KeymapManager.module.exports.KeymapManager.dispatchCommandEvent (/Applications/Atom Beta.app/Contents/Resources/app/node_modules/atom-keymap/lib/keymap-manager.js:621:22)
at KeymapManager.module.exports.KeymapManager.handleKeyboardEvent (/Applications/Atom Beta.app/Contents/Resources/app/node_modules/atom-keymap/lib/keymap-manager.js:412:28)
at WindowEventHandler.handleDocumentKeyEvent (/Applications/Atom Beta.app/Contents/Resources/app/src/window-event-handler.js:108:40)
```

### Commands

```
4x -2:23.7.0 core:confirm (input.hidden-input)
-0:36.9.0 pane:show-next-recently-used-item (atom-workspace.workspace.scrollbars-visible-always.theme-one-dark-syntax.theme-one-dark-ui.teletype-Guest)
-0:36.8.0 pane:move-active-item-to-top-of-stack (atom-workspace.workspace.scrollbars-visible-always.theme-one-dark-syntax.theme-one-dark-ui.teletype-Guest)
-0:33.4.0 pane:show-next-recently-used-item (input.hidden-input)
-0:33.2.0 pane:move-active-item-to-top-of-stack (div.panels-item)
-0:28.2.0 pane:show-next-recently-used-item (input.hidden-input)
-0:28.1.0 pane:move-active-item-to-top-of-stack (input.hidden-input)
2x -0:25.8.0 editor:newline (input.hidden-input)
-0:19.8.0 editor:select-to-beginning-of-word (input.hidden-input)
-0:17.9.0 command-palette:toggle (input.hidden-input)
-0:15.5.0 core:confirm (input.hidden-input)
-0:15.5.0 figlet:convert (input.hidden-input)
6x -0:14.6.0 core:move-up (input.hidden-input)
-0:13.5.0 core:confirm (input.hidden-input)
-0:11.9.0 editor:consolidate-selections (input.hidden-input)
-0:11.9.0 core:cancel (input.hidden-input)
```

### Non-Core Packages

```
advanced-open-file 0.16.7
atom-notes 1.14.2
atom-terminal 0.8.0
autocomplete-python 1.10.3
autocomplete-xml 0.9.4
busy-signal 1.4.3
change-case 0.6.5
custom-title 1.0.1
figlet 0.5.4
file-icons 2.1.13
geiger 2.1.0
git-plus 7.10.0
git-time-machine 1.5.9
gutter-shadow 1.1.0
highlight-selected 0.13.1
indent-guide-improved 1.4.13
intentions 1.1.5
language-docker 1.1.8
language-groovy 0.7.0
language-powershell 4.0.0
language-puppet 0.23.0
language-tcl 0.1.2
less-than-slash 0.17.0
linter 2.2.0
linter-js-yaml 1.2.8
linter-puppet-lint 0.8.4
linter-puppet-parser 0.1.1
linter-pylint 2.1.0
linter-ui-default 1.6.10
markdown-writer 2.7.3
merge-conflicts 1.4.5
minimap 4.29.7
minimap-bookmarks 0.4.2
minimap-cursorline 0.2.0
minimap-find-and-replace 4.5.2
minimap-git-diff 4.3.1
minimap-highlight-selected 4.6.1
minimap-selection 4.5.0
minimap-split-diff 0.3.7
project-manager 3.3.5
project-plus 1.0.0
react 0.17.0
rename-tabs 0.2.0
revert-buffer 0.6.0
sort-lines 0.18.0
split-diff 1.5.1
sync-settings 0.8.3
tabularize 0.2.5
teletype 0.1.2
valign 1.1.3
wordcount 2.10.4
```