Integrate tslint

[egamma]

This PR integrates tslint.

It adds:

• a tslint.json file. The rules defined in the tslint.json file are currently minimal. The only rule enabled is the no-unused-variable.
• gulp tslint runs tslint across the vscode base.
• a task to run tslint from inside Code.
• the microsoft tslint rule extensions. The rules are currently not used, but they will enable us to use rules like promise-must-complete.

To get tslint checking as you type you need to install the vscode-tslint.

[bpasero]

The rules I used for selfhost once are:

{
    "rules": {
        "no-duplicate-variable": true,
        "no-unreachable": true,
        "no-unused-expression": true,
        "no-unused-variable": true,
        "no-var-keyword": true,
        "no-use-before-declare": true,
        "curly": true,
        "semicolon": true
    }
}

[egamma]

Looks like the build failed due to an error in getting oniguruma.