Cypress: 0.17.2

*Released 09/06/2016* **Notes:** - After this update if you are seeing `<iframe>` origin errors *please let us know* by [opening an issue](https://github.com/cypress-io/cypress/issues/new). We will screen-share with you to diagnose the issue. We're no longer aware of any situation where this should happen, so if you're experiencing these bugs, please help us track them down. **Features:** - Attempting to [cy.visit()](https://on.cypress.io/visit) a non `text/html` resource will now throw a specific error message instead of bombing on page injection with an `<iframe`> origin error. You have to visit actual `html`, you cannot visit something like a `.json` or `.png`. If you're wanting to visit an API route on your backend that does something like set cookies (thus avoiding loading your UI) you can just use [cy.request()](https://on.cypress.io/request) for this since it will now automatically get and set cookies under the hood. Fixes [#211](https://github.com/cypress-io/cypress/issues/211). **Bugfixes:** - Fixed a regression in `0.17.1` that was incorrectly setting `Cache` headers. This *could* cause a situation where you received an `<iframe>` origin error. Additionally we now set `No-Cache` headers whenever we inject content, but otherwise respect the headers coming from web servers. When using Cypress as the file server, we set `etags` but prevent caching. - Most likely fixed a bug that was crashing Cypress due to `Cannot set headers after they've been sent`. We were unable to write a test for this since we could not recreate the error, but analyzed how it *may* happen and fixed the code there. {% open_an_issue %} if you see this error, it will be obvious since Cypress will literally crash. - We stopped minifying `vendor.js` (for real this time). More optimizations to come around this. - Prevented accidentally setting `domain` cookies when they were really `hostOnly` cookies, thus duplicating the number of cookies sent on requests. Kudos to [@bahmutov](https://github.com/bahmutov) for finding this one. Fixes [#207](https://github.com/cypress-io/cypress/issues/207). - Fixed some edge cases in `cypress-core-extension` where it threw errors when attempting to `executeScript` on a tab with `about:blank` or `chrome://` urls. - We've fixed some underlying issues with [cy.go()](https://on.cypress.io/go) during `cypress run`. It always worked fine in real Chrome. Previously there were some situations where it would not navigate forward / back correctly. **Misc:** - No longer force [cy.visit()](https://on.cypress.io/visit) to navigate to `about:blank` prior to navigating to the real url. Fixes [#208](https://github.com/cypress-io/cypress/issues/208). - [cy.writeFile()](https://on.cypress.io/writefile) can now accept an empty string. Fixes [#206](https://github.com/cypress-io/cypress/issues/206). - Improved error messages for [cy.readFile()](https://on.cypress.io/readfile) and [cy.writeFile()](https://on.cypress.io/writefile). - The full file path is now included in console output for [cy.readFile()](https://on.cypress.io/readfile) and [cy.writeFile()](https://on.cypress.io/writefile). - The [Kitchen Sink](https://github.com/cypress-io/cypress-example-kitchensink) and `example_spec.js` have been updated to reflect the newest changes and features of `0.17.1`.