Browser ie11

Updates for specs and docs, and an optional last commit which is explained below:

Apparently after we decided on just doing the `Browser.modernie` thing in all builds, some people suddenly started having issues with it anyway. I don't feel like going through all of this again, so the last commit in my branch supports a second option we have.

Summary:

* Current state (1.4.5):
  - IE11 detection broken

* Desired state (1.5):
  - Option 1:
    + For all builds: Differentiate between IE>=10 (`Browser.ie`) and IE<=11 (`Browser.modernie`). This is to protect people from "just" using `Browser.ie` and treating them equally bad.
  - Option 2:
    + For no-compat build: Fix IE11 detection (i.e. all IE is once again `Browser.ie`). This is technically+semantically correct.
    + For compat build: Differentiate between IE>=10 (`Browser.ie`) and IE<=11 (`Browser.modernie`). This is to make sure we don't break existing projects that (implicitly or explicitly) rely on `Browser.ie` being falsy for IE11.
  - Option 3:
    + For all builds: Fix IE11 detection (i.e. all IE is once again `Browser.ie`). **Breaking change,** so this is not feasible, the compat build should remain compatible.
  - Option 4:
    + For no-compat build: `Browser.ie` is true.
    + For compat build: `Browser.ie` is `undefined`.

* State of pull request:
  - Implemented option 4: Least amount of changes since 1.4. Fixes the IE11 issue in the most conservative way, until a decision is reached regarding the other option(s).
  - Ready to be pulled.