1.17.2: add hyperlinks support and revert setupterm(os.devnull)

[jquast]

• move "styles" section from colors.rst to terminal.rst
• add term.link("https://example.com", "example.com") hyperlink support
• add bin/cnn.py news example
• revert this setupterm() experiment remove documentation about speciality of setupterm's descriptor, use os.devnull #59, discussed in ValueError: I/O operation on closed file #146
• ignore ValueError for multiprocessing environments ValueError: I/O operation on closed file #146

[codecov]

Codecov Report

Merging #147 into master will decrease coverage by 4%.
The diff coverage is 86.66%.

@@            Coverage Diff             @@
##           master     #147      +/-   ##
==========================================
- Coverage   95.86%   91.86%   -4.01%     
==========================================
  Files           8        8              
  Lines         968      946      -22     
  Branches      153      154       +1     
==========================================
- Hits          928      869      -59     
- Misses         36       66      +30     
- Partials        4       11       +7

Impacted Files	Coverage Δ
blessed/_capabilities.py	81.81% <100%> (-18.19%)	⬇️
blessed/terminal.py	96.07% <85.71%> (-2.98%)	⬇️
blessed/win_terminal.py	0% <0%> (-33.34%)	⬇️
blessed/keyboard.py	96.2% <0%> (-3.8%)	⬇️
blessed/sequences.py	98.13% <0%> (-1.87%)	⬇️
blessed/formatters.py	98.48% <0%> (-1.52%)	⬇️
blessed/color.py	100% <0%> (ø)	⬆️

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 75e3890...840032f. Read the comment docs.