Remove unneeded NameObject.__init__ method in generic.py.

Because `NameObject` is a subclass of `str`, it doesn't need an `__init__` method, so I took it out.  To skip the explanations, go to **What I did**, below.

The explanation I read said that because `str` is an immutable type, it gets its value in its `__new__`, and the `__init__` is just a no-op.  Here are three previous versions of `NameObject.__init__`:

The original:
```
class NameObject(str, PdfObject):
    ...
    def __init__(self, data):
        str.__init__(data)
```

This is just not the way to call your superclass's initializer, but as I said, `str.__init__` is a no-op, so this didn't harm anything.

The next version was never in a released version, but it's the best, in commit 7843fb2 by shezadkhan137:
```
class NameObject(str, PdfObject):
    ...
    def __init__(self, data):
        super(NameObject, self).__init__(data)
```

This is absolutely correct, but it caused an error!  The reason is that the `PdfObject` class does not have an `__init__` method, and `object`, the superclass of `PdfObject`, has an `__init__` method, but with no parameter to match `data` (only `self`, which is implicit here).  This could have been fixed by calling `super(NameObject, self).__init__()`, which would have called `PdfObject`'s `__init__`, if it had one, but it doesn't, so it would have called `object.__init__` with no extra argument, which wouldn't be an error, but does nothing anyway.

The most recent state of things was d31ea04, also by shezadkhan137:
```
class NameObject(str, PdfObject):
    ...
    def __init__(self, data):
        str.__init__(super(NameObject, self).__new__(str, data))
```

What this does is create an extra `str` and call the no-op `__init__` on that, which is harmless but pointless on all three Pythons.

<h3>What I did</h3>

1) Removed the `__init__` method completely from `NameObject`.
2) also in NameObject, I did this "just because!":
```
-    delimiterCharacters = b_("("), b_(")"), b_("<"), b_(">"), b_("["), b_("]"), b_("{"), b_("}"), b_("/"), b_("%")
+    delimiterCharacters = tuple(b_(c) for c in "()<>[]{}/%")
```
3) Tested on CPython 2.7.3, CPython 3.3, and PyPy 2.7.3 [PyPy 2.2.1]
4) Put `.DS_Store` in `.gitignore`.  It's a Mac thing.