Improve method names parsing

[macbre]

2017-06-24 15:24:07 dataflow                            ERROR    Unable to parse method name: WallThread:getReplyIdsFromDB
Traceback (most recent call last):
  File "/home/macbre/github/query-digest/digest/dataflow.py", line 82, in data_flow_format_entry
    (target, edge) = method.rsplit('::', 1)
ValueError: need more than 1 value to unpack
2017-06-24 15:24:07 dataflow                            ERROR    Unable to parse method name: wfGetWikiaPageProp
Traceback (most recent call last):
  File "/home/macbre/github/query-digest/digest/dataflow.py", line 82, in data_flow_format_entry
    (target, edge) = method.rsplit('::', 1)
ValueError: need more than 1 value to unpack
2017-06-24 15:24:07 dataflow                            ERROR    Unable to parse method name: {closure}
Traceback (most recent call last):
  File "/home/macbre/github/query-digest/digest/dataflow.py", line 82, in data_flow_format_entry
    (target, edge) = method.rsplit('::', 1)
ValueError: need more than 1 value to unpack
2017-06-24 15:24:07 dataflow                            ERROR    Unable to parse method name: DPLMain:dynamicPageList
Traceback (most recent call last):
  File "/home/macbre/github/query-digest/digest/dataflow.py", line 82, in data_flow_format_entry
    (target, edge) = method.rsplit('::', 1)
ValueError: need more than 1 value to unpack
2017-06-24 15:24:07 dataflow                            ERROR    Unable to parse method name: AjaxPollClass:getVotes
Traceback (most recent call last):
  File "/home/macbre/github/query-digest/digest/dataflow.py", line 82, in data_flow_format_entry
    (target, edge) = method.rsplit('::', 1)
ValueError: need more than 1 value to unpack
2017-06-24 15:24:07 dataflow                            ERROR    Unable to parse method name: wfSetWikiaPageProp
Traceback (most recent call last):
  File "/home/macbre/github/query-digest/digest/dataflow.py", line 82, in data_flow_format_entry
    (target, edge) = method.rsplit('::', 1)
ValueError: need more than 1 value to unpack