Integrate content from busiing:master

[p-snft]

Replaces #3, which broke the original plotting functionality.

[pep8speaks]

Hello @p-snft! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file oemof_visio/plot.py:

Line 172:80: E501 line too long (118 > 79 characters)
Line 178:28: E231 missing whitespace after ','
Line 181:80: E501 line too long (115 > 79 characters)
Line 183:30: E231 missing whitespace after ','
Line 187:80: E501 line too long (115 > 79 characters)
Line 203:80: E501 line too long (81 > 79 characters)
Line 206:80: E501 line too long (80 > 79 characters)
Line 209:80: E501 line too long (81 > 79 characters)
Line 225:80: E501 line too long (100 > 79 characters)
Line 230:80: E501 line too long (118 > 79 characters)
Line 244:80: E501 line too long (85 > 79 characters)
Line 247:21: E231 missing whitespace after ','
Line 247:26: E231 missing whitespace after ','
Line 250:80: E501 line too long (144 > 79 characters)
Line 418:80: E501 line too long (86 > 79 characters)
Line 493:80: E501 line too long (89 > 79 characters)
Line 496:80: E501 line too long (102 > 79 characters)
Line 502:80: E501 line too long (89 > 79 characters)

[p-snft]

@busiing: I tried to integrate this but I am a bit lost. Can you provide an example on how to use this? (As I understand it, it should somehow automatically create plots or many nodes within one figure - and also speed up the rendering process.)