Fix class inheritance

Previously, the inheritance informations were lost when the class
was declared using a class expression (rather than a class
declaration) and was redefining the constructor method without
calling `super`.
Fix code generation with hoisted variables on 'instantiate' builds

Traceur was generating an function expression, but for some reason it
was interpreting the function body as an expression list rather than
a statement list. This commit enforce the right parsing by using
ParseTreeFactory's primitives.
Add tests for #1084 and #1085
Add my name to the AUTHORS file