Compose chars conflict with meta keys

• I am on the latest Hyper.app version (I am not, I've built it myself.)
• I have searched the issues of this repo and believe that this is not a duplicate

• OS version and name: macOS 10.12.1
• Hyper.app version: aa410812a55b66c9fb53443b75345395357a1973
• Link of a Gist with the contents of your .hyper.js: N/A, default config with modifierKeys: { altIsMeta: true }
• The issue is reproducible in vanilla Hyper.app: Yeah.

Issue

In #686, support for using alt as meta on osx was added. In #1006, support for composed chars, including using alt+n to type ~ on my keyboard was added.

Unfortunately, both settings conflict with each other. If I use alt as a meta key, I can no longer use alt+n to type ~. This is somewhat expected, but iTerm found a way around this and it would be super handy if Hyper could do as well!

Review the behavior described in issues #686 and #1006, then reproduce it on macOS with the default .hyper.js setting modifierKeys: { altIsMeta: true }. The issue is done when alt+n can compose ~ while Alt continues to function as a Meta key, matching the requested iTerm behavior.