A guide to differences between v8 versions 3.28.73 and 3.14.5.9

I'm trying to compile a node.js extension module against node-v0.12.2 and some v8 3.28.73 classes had lost methods which were there in version 3.14.5.9 (used in node-v0.10.10). Of course, this is only one of the errors I'm facing. The error message follows

‘AsciiValue’ is not a member of ‘v8::String’. 

The function which calls the method is very short

char * getStringArg(v8::Local<v8::Value> value) 
{
    v8::String::AsciiValue string(value);
    char *str = (char *) malloc(string.length() + 1);
    strcpy(str, *string);
    return str;
}

Where can I find a guide to the big differences between these v8 versions?

I'm advancing by way of trial and error.