Open current markdown file in a new window

It works for saved and unsaved files. Maybe unsaved file's content
should be written to a temporary file in case we crash, so that the user
doesn't lose all it's content.

MarkdownLivePreview.py

@@ -0,0 +1,64 @@
+import sublime
+import sublime_plugin
+
+from .utils import *
+
+def plugin_loaded():
+    pass
+
+class MdlpInsertCommand(sublime_plugin.TextCommand):
+
+    def run(self, edit, point, string):
+        self.view.insert(edit, point, string)
+
+class OpenMarkdownPreviewCommand(sublime_plugin.TextCommand):
+
+    def run(self, edit):
+
+        """ If the file is saved exists on disk, we close it, and reopen it in a new
+        window. Otherwise, we copy the content, erase it all (to close the file without
+        a dialog) and re-insert it into a new view into a new window """
+
+        original_view = self.view
+        file_name = original_view.file_name()
+
+        syntax_file = original_view.settings().get('syntax')
+
+        if file_name is None:
+
+            # the file isn't saved, we need to restore the content manually
+            total_region = sublime.Region(0, original_view.size())
+            content = original_view.substr(total_region)
+            original_view.erase(edit, total_region)
+            original_view.close()
+
+            # FIXME: save the document to a temporary file, so that if we crash,
+            #        the user doesn't lose what he wrote
+
+        else:
+            original_view.close()
+
+        sublime.run_command('new_window')
+        window = sublime.active_window()
+
+        window.run_command('set_layout', {
+            'cols': [0.0, 0.5, 1.0],
+            'rows': [0.0, 1.0],
+            'cells': [[0, 0, 1, 1], [1, 0, 2, 1]]
+        })
+
+        window.focus_group(0)
+        if file_name:
+            new_view = window.open_file(file_name)
+        else:
+            new_view = window.new_file()
+            new_view.run_command('mdlp_insert', {'point': 0, 'string': content})
+
+        new_view.set_syntax_file(syntax_file)
+
+    def is_enabled(self):
+        # FIXME: is this the best way there is to check if the current syntax is markdown?
+        #        should we only support default markdown?
+        #        what about "md"?
+        return 'markdown' in self.view.settings().get('syntax').lower()
+