Failures of the is-regexp library result in spectacular crashes

[joydeep-b]

https://console.cloud.google.com/errors/CJfe1s-Vv9-01AE?project=arjunguha-research-group

Stack trace:

Error: Symbol(Symbol.toStringTag) is not defined
    at Object.get (main.bundle.js:263)
    at Proxy.toString (<anonymous>)
    at ./node_modules/is-regexp/index.js.module.exports.input (main.bundle.js:136037)
    at stringify (main.bundle.js:316505)
    at ret.{.tokens.newLine.objKeys.map (main.bundle.js:316541)
    at Array.map (<anonymous>)
    at stringify (main.bundle.js:316536)
    at ./src/stringifyObject.ts.module.exports (main.bundle.js:316557)
    at OutputPanel.log (main.bundle.js:314361)
    at Sandbox.onResult (main.bundle.js:315972)
    at Object.get (main.bundle.js:263)
    at Proxy.toString (<anonymous>)
    at ./node_modules/is-regexp/index.js.module.exports.input (main.bundle.js:136037)
    at stringify (main.bundle.js:316505)
    at ret.{.tokens.newLine.objKeys.map (main.bundle.js:316541)
    at Array.map (<anonymous>)
    at stringify (main.bundle.js:316536)
    at ./src/stringifyObject.ts.module.exports (main.bundle.js:316557)
    at OutputPanel.log (main.bundle.js:314361)
    at Sandbox.onResult (main.bundle.js:315972)
    at main.bundle.js:159077

[joydeep-b]

Suggest removing the silly is-regexp dependency and replacing with a more robust, exception free version.

[sp1tz]

We could probably just use what comes free with Lodash.