All HTML attributes are lowercased per HTML spec. This means that we have to convert dash case to camel case. a-b => aB

See:
https://github.com/angular/angular/blob/94e203b9df6c4b79ba30f1f08fc54ff919f722e1/modules/angular2/src/core/compiler/pipeline/property_binding_parser.js

https://github.com/angular/angular/blob/master/modules/angular2/src/core/compiler/pipeline/element_binder_builder.js