select: option groups are not read by JAWS/IE

[benjiallen]

What is the expected behavior?

Option groups should be read by screen readers.

What is the current behavior?

Option groups are not read by screen readers.

Steps to reproduce the issue:

AngularJS Material Demo which shows your issue:

• Open up IE and JAWS and navigate to the right place in the page
• Open the "topping" select menu
• Observe that the option groups are not read by JAWS e.g., "meats", "veggies"

What is the use-case or motivation for changing an existing behavior?

This component is not accessible to screen reader users in it's current form.

Which versions of AngularJS, Material, OS, and browsers are affected?

• Version of AngularJS: 1.6.7 (this is the version used in the demo site)
• Version of Material: 1.1.8 (this is the version used in the demo site)
• OS: Windows 7 Enterprise
• Browsers: IE11
• Screen reader: JAWS 17