IE11 compatibility problem

[tomczhang]

As usual, typechecker will be used as a dependecies. And typechecker doesn't transfer the index.ts to es5, such as line 254 has the keyword "const".

If webpack has a setting which has "exclude: /node_modules/", the output js won't work well in IE11.

[balupton]

which ecmascript version would you want to target for web browsers? boundation is setup for typescript projects to target the ecmascript version of the previous year - which should be suitable for evergreen browsers - if you can propose an alternative for this complexity, and why you are targetting non-evergreen browsers - then something can be considered