Parse Pd files using user defined filters.
	
	>>> p = PdParser("patches/parser-test.pd")
	>>> def found(canvasStack, type, action, bits):
	...   print "canvasStack:", canvasStack, "type:", type, "action:", action, "arguments:", bits
	... 
	>>> p.add_filter_method(found, canvas="REFERENCE", type="#X", action="text")
	>>> p.add_filter_method(found, canvas="semicolon-test", type="#X", action="msg")
	>>> p.add_filter_method(found, object="osc~")
	>>> p.parse()
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 135 336 Tags: tag_one \, tag_two
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 115 301 Description: Some kind of verbose description here.
	<BLANKLINE>
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 114 121 Name: thing
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 114 174 Argument 0: first argument (required)
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 114 194 Argument 1: second argument (optional)
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 114 214 Inlet 0: my first inlet is blah
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 114 234 Inlet 1: msg1 <msg1arg>: what this message does. msg2
	<msg2arg>: what this other message does \, default 0 which is the default
	<BLANKLINE>
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 114 278 Outlet 0: what comes out the second outlet.
	canvasStack: ['patches/parser-test.pd', 'REFERENCE'] type: #X action: text arguments: 113 141 Summary: what this thing does is blah blah blah
	canvasStack: ['patches/parser-test.pd'] type: #X action: obj arguments: 471 83 osc~ 220
	canvasStack: ['patches/parser-test.pd', 'semicolon-test'] type: #X action: msg arguments: 10 18 this is a message box \, with comments \, and also \;
	semicolons! yes it is. it's like this: yo. test \; test \; test \;
	<BLANKLINE>
	canvasStack: ['patches/parser-test.pd'] type: #X action: obj arguments: 633 213 osc~ 440
	49