Update CI/CD & Fix bugs

[MKoesters]

Update CI/CD

• adapted plot.py and tests to newer plotly version
• adapdated obo detection to work with python 3.5
• run tests with tox
• build docu with tox
• run example scripts using tox
• run codecoverage using tox
• configure travis to use tox envs
• configure appveyor to use tox envs
• configure travis to deploy package to pypi on tag
• update .gitignore
• update requirements, docs/requirements and add requirements_dev
• codecov will post change in coverage under pull requests
• add pre-commit config to run common style fixes and black

[codecov[bot]]

Codecov Report

Merging #146 into master will increase coverage by 65.89%. The diff coverage is 100%.

@@             Coverage Diff             @@
##           master     #146       +/-   ##
===========================================
+ Coverage   15.94%   81.83%   +65.89%     
===========================================
  Files          13       32       +19     
  Lines        1844     3397     +1553     
===========================================
+ Hits          294     2780     +2486     
+ Misses       1550      617      -933

Impacted Files	Coverage Δ
tests/plot_spec_test.py	98.38% <ø> (ø)
pymzml/run.py	82.71% <100%> (+66.04%)	:arrow_up:
pymzml/plot.py	73.3% <100%> (+66.19%)	:arrow_up:
tests/main_spec_test.py	98.87% <0%> (ø)
tests/file_io_indexed_gzip_writer_test.py	99% <0%> (ø)
tests/main_ms_numpress_ext_test.py	97.41% <0%> (ø)
tests/main_reader_test.py	99.29% <0%> (ø)
tests/file_io_standard_gzip_test.py	96.29% <0%> (ø)
tests/ms2_spec_test.py	96.15% <0%> (ø)
... and 21 more

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