More changes to be compatible with python 3

[daurer]

• Use specific utf-8 encoding
• avoid deprecated functions such as xrange, buffer, bytes

[codecov-io]

Codecov Report

Merging #116 into master will increase coverage by 8.29%. The diff coverage is 5.55%.

@@            Coverage Diff             @@
##           master     #116      +/-   ##
==========================================
+ Coverage   11.96%   20.25%   +8.29%     
==========================================
  Files          67       79      +12     
  Lines        6588     8972    +2384     
==========================================
+ Hits          788     1817    +1029     
- Misses       5800     7155    +1355

Impacted Files	Coverage Δ
src/interface/ui/data_window.py	11.73% <ø> (ø)	:arrow_up:
src/interface/zmqsocket.py	38.7% <0%> (+0.61%)	:arrow_up:
src/interface/ui/plotdata_table.py	10.95% <0%> (ø)	:arrow_up:
src/interface/ringbuffer.py	20.39% <0%> (ø)	:arrow_up:
src/interface/data_source.py	18.28% <0%> (ø)	:arrow_up:
src/ipc/zmqserver.py	21.29% <0%> (-0.2%)	:arrow_down:
src/interface/Qt.py	54.19% <100%> (+0.35%)	:arrow_up:
src/backend/__init__.py	100% <0%> (ø)	:arrow_up:
src/hummingbird.py	0% <0%> (ø)	:arrow_up:
src/backend/pint/measurement.py	22.41% <0%> (ø)
... and 12 more

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