provide == as well as isequal for Julia 0.3

[stevengj]

Currently, you are providing an isequal method for various types (e.g. StringNode). In Julia 0.3, you will also need to provide ==. See JuliaLang/julia#6833.

(In Julia 0.2, == called isequal by default, so providing isequal was enough. In Julia 0.3, however, these two functions are swapped: isequal calls == by default. So overriding isequal is not enough to make things like != or == work. In order to remain backward-compatible with Julia 0.2, you will need to provide both methods.)