Replace deprecated attrdict with local version

A boilerplate implementation of the access by member for keys helps
solving the issue of unmaintained AttrDict. Its a reasonable
workaround for now.

Author: wallento

setup.py

@@ -22,7 +22,6 @@
 # Fields marked as "Optional" may be commented out.
 
 requires = ["svgwrite",
-            "attrdict",
             "six" # 2 and 3 compatibility
             ]
 setup(

test/diff.py

@@ -3,7 +3,6 @@
 
 import xmldiff
 import xmldiff.main
-from attrdict import AttrDict
 from lxml import etree
 
 from PIL import Image, ImageChops

wavedrom/attrdict.py

@@ -0,0 +1,4 @@
+class AttrDict(dict):
+    def __init__(self, *args, **kwargs):
+        super(AttrDict, self).__init__(*args, **kwargs)
+        self.__dict__ = self

wavedrom/base.py

@@ -2,8 +2,7 @@
 # SPDX-License-Identifier: MIT
 
 import svgwrite
-from attrdict import AttrDict
-
+from .attrdict import AttrDict
 
 class SVGBase(object):
     container = AttrDict({

wavedrom/css.py

@@ -4,8 +4,8 @@
 # Translated to Python from original file:
 # https://github.com/drom/wavedrom/blob/master/src/WaveDrom.js
 
-import attrdict
-css = attrdict.AttrDict({})
+from .attrdict import AttrDict
+css = AttrDict({})
 css.default = """
 text{font-size:11pt;
      font-style:normal;

wavedrom/tspan.py

@@ -4,7 +4,6 @@
 import sys
 
 import svgwrite
-from attrdict import AttrDict
 from six import string_types
 from svgwrite.base import BaseElement
 from svgwrite.etree import etree

wavedrom/waveform.py

@@ -10,7 +10,7 @@
 import re
 from itertools import chain
 import svgwrite
-from attrdict import AttrDict
+from .attrdict import AttrDict
 from collections import deque
 
 from six import string_types