Underline with yellow line for not used variables

[paulvi]

Just like in JDT, when variable is not used, it is underlined

int underfinedVar;
~~~~~~~~~~~

initially raised as Nodeclipse/nodeclipse#170

This is other example of Eclipse users expect JavaScript features to be like in JDT.

The first example was my emotional #140 as Eclipse user I did not expect hint for literals.

[angelozerr]

It's feature for https://github.com/angelozerr/tern-lint. Please move this issue to tern-lint. Thank's!

[angelozerr]

See https://github.com/angelozerr/tern.java/wiki/New-and-Noteworthy-0.7.0#lint-unused-variablefunction for more info