Variables in snippets now being treated as placeholders

[adbertram]

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System Details

• Operating system name and version: macOS Sierra
• VS Code version: 1.8
• PowerShell extension version: 0.7.2
• Output from $PSVersionTable: PS v6 alpha 13

Issue Description

Variables inside of PowerShell snippets are now being treated as placeholders. For example, these are the exact same thing now:

$var
${var}

[adbertram]

To get around this, I've had to replace all PowerShell variables with double $. They are still treated as placeholders but if I don't change them, at least they stay that way.

[daviwil]

Fixed with #384, it'll be in today's update!