Syntax highlight bug: 0 #:: Stream(1)

The following code gets highlighted incorrectly:

```scala
0 #:: Stream(1)
```

The second `:` is not being highlighted as part of the method name, even though it is.

[Demo](https://github-lightshow.herokuapp.com/?utf8=%E2%9C%93&scope=from-url&grammar_url=https%3A%2F%2Fgithub.com%2Fatom-community%2Flanguage-scala%2Fblob%2Fv1.1.9%2Fgrammars%2Fscala.cson&grammar_text=&code_source=from-url&code_url=https%3A%2F%2Fgist.githubusercontent.com%2Fmkantor%2F127b02ac08b37e42ca84610b34cfb824%2Fraw%2F8f3172896fbafd31db7f81249e4bed9aaec2aeb4%2FStreamConcatenationOperator.scala&code=).

This exact same bug is present in the Scala TextMate bundle (mads-hartmann/scala.tmbundle/issues/60), which is currently used by [Linguist](https://github.com/github/linguist), so you'll see the same problem in the code block above.

Start with grammars/scala.cson and reproduce the highlighted output for `0 #:: Stream(1)`. Check how the Scala TextMate bundle handles the method name, then verify that both colons are highlighted as part of it.

Written by the indexing model from the issue text.