nan: auto-delete weak callback object

* Check with IsNearDeath() if it's safe to delete the weak callback
  context object.

* Turn _NanWeakCallbackData::Dispose() into a deprecated no-op,
  resource management is now handled automatically.

Incidentally fixes a double-free bug when the user calls Dispose()
twice.
Merge pull request #121 from bnoordhuis/persistent-isneardeath-auto-cleanup

nan: auto-delete weak callback object
updated readme
1.1.0
nan: declare inner callback in `NAN_WEAK_CALLBACK`

Fixes OS X LLVM compiler error:

    N_WEAK_CALLBACK(write_object_cb) {
    ^
    ../node_modules/nan/nan.h:779:9: note: expanded from macro 'NAN_WEAK_CALLBACK'
            _Nan_Weak_Callback_ ## name(wcbd);                                     \
            ^
    <scratch space>:236:1: note: expanded from here
    _Nan_Weak_Callback_write_object_cb
    ^
    ../src/binding.cc:187:87: note: in instantiation of function template specialization '<anonymous namespace>::write_object_cb<v8::Object, void>' requested here
        _NanWeakCallbackInfo<Object, void>* info = NanMakeWeakPersistent(val, user_data, &write_object_cb<Object, void>);
                                                                                          ^
    ../src/binding.cc:150:1: note: '_Nan_Weak_Callback_write_object_cb' should be declared prior to the call site or in an associated namespace of one of its arguments
    NAN_WEAK_CALLBACK(write_object_cb) {
    ^
    ../node_modules/nan/nan.h:784:28: note: expanded from macro 'NAN_WEAK_CALLBACK'
        static NAN_INLINE void _Nan_Weak_Callback_ ## name(                        \
                               ^
    <scratch space>:2:1: note: expanded from here
    _Nan_Weak_Callback_write_object_cb
    ^
    1 error generated.

Special thanks to @kkoopa for coming up with the patch.
I'm just submitting it.

See https://github.com/TooTallNate/ref/pull/14 for more details.
Add NanSetPrototypeTemplate
Add NanSetPrototypeTemplate()
prep for 1.1.1
1.1.1
Update NanSetPrototypeTemplate()

Merged to one function, that uses NanSetTemplate() which does the version splitting.
1.1.2 prep
1.1.2
Added SetPrototypeTemplate() test cases
Added new Scope to Init function
adjusted accordingly #128
Fix broken anchors in README.md
Linting
Removed cflags
Merge pull request #131 from rvagg/warning

Removed cflags
Merge pull request #130 from rvagg/readme_fix

Fix broken anchors in README.md