[ruby] add support for non-interpolated (and others) heredoc syntax

[aeschli]

From @rgl on April 11, 2016 8:13

• VSCode Version: 0.10.11.
• OS Version: Windows 10.

Currently Code supports the Here Documents (aka heredoc) using this syntax:

But the following are not supported:

See the exact details about the Here Documents at the Ruby Manual and also other examples.

Copied from original issue: microsoft/vscode#5155

[aeschli]

the <<HEREDOC syntax seems to work now (there has been a recent update).
But I can reproduce the issue for <<-'EXPECTED'

[koenpunt]

Also, interpolated variables are seen as comments in heredoc blocks: