Buffer: Split only complete lines ending with \r\n

This change is required for Turtle output generated by the Python environment. Otherwise, drawing some images could add empty new lines (in the browser), since the original JSON message got split between the ending \r\n characters.

lib/runner/connection/buffer.rb

@@ -6,7 +6,7 @@ class Runner::Connection::Buffer
   # substring either in single or double quotes (e.g., within a JSON). Originally, each line break consists of `\r\n`.
   # We keep the `\r` at the end of the line (keeping "empty" lines) and replace it after buffering.
   # Inspired by https://stackoverflow.com/questions/13040585/split-string-by-spaces-properly-accounting-for-quotes-and-backslashes-ruby
-  SPLIT_INDIVIDUAL_LINES = /(?:"(?:\\"|[^"])*"|'(?:\\'|[^'])*'|[^\n])+/
+  SPLIT_INDIVIDUAL_LINES = /(?:"(?:\\"|[^"])*"|'(?:\\'|[^'])*'|(?:[^\r\n]|\r(?=\n)))+/
 
   def initialize
     @global_buffer = +''