Adapter methods fail when the original method has a parameter

[basil]

Fixes #69. The new test fails without the changes to src/main and passes with them. The problem is that the logic for pushing arguments to the stack

for (Type p : paramTypes) {
    mv.visitVarInsn(p.getOpcode(ILOAD), sz);
    sz += p.getSize();
}

assumes that we didn't previously call

if (hasAdapterMethod()) {
    // the LHS of the adapter method invocation
    ga.loadThis();
    sz++;
}

a few lines earlier. If we did, then sz will have been incremented by one for the LHS of the adapter method invocation and we will be off by one. This PR corrects the off-by-one error by accounting for whether or not an adapter method is present.

[kohsuke]

I agree with the substance of the change. I left one comment as a suggestion to make the intent a little clearer (which led to this bug in the first place)