Support all VTK readers

[banesullivan]

This PR creates a way to support all VTK reader classes by mapping them to file extensions.

This creates a standard routine for reading any VTK supported file with just a few lines of code and without having to remember the proper VTK classes for performing those reads.

Find the dictionary mapping the extensions to the proper VTK reader classes in readers.py.

import vtki
filename = 'path/to/my/file.ext'
data = vtki.read(filename)

Perhaps you need some flexibility with what the reader performs and need to call several setters/options on the reader - then simply pass a dictionary of function names and parameters to pass:

import vtki
filename = 'path/to/my/file.ext'
data = vtki.read(filename, attrs={'DebugOn':None, 'SetScalarsName':'foo'})

NOTES:

• Time-varying readers are not yet supported in this but could be implemented down the road
• These need to be double checked by people familiar with all the different formats
• The list of readers is not complete but creates a simple framework to add new ones by simply adding a key-value pair in the READERS dictionary.

[codecov]

Codecov Report

Merging #100 into master will decrease coverage by 0.34%.
The diff coverage is 75%.

@@            Coverage Diff             @@
##           master     #100      +/-   ##
==========================================
- Coverage   87.58%   87.23%   -0.35%     
==========================================
  Files          16       17       +1     
  Lines        4220     4254      +34     
==========================================
+ Hits         3696     3711      +15     
- Misses        524      543      +19

Impacted Files	Coverage Δ
vtki/container.py	96.58% <100%> (+0.01%)	⬆️
vtki/utilities.py	93.42% <100%> (+0.05%)	⬆️
vtki/__init__.py	97.05% <100%> (+0.08%)	⬆️
vtki/pointset.py	91.17% <100%> (ø)	⬆️
vtki/readers.py	71.05% <71.05%> (ø)

---

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[codecov]

Codecov Report

Merging #100 into master will decrease coverage by 0.08%.
The diff coverage is 87.64%.

@@            Coverage Diff             @@
##           master     #100      +/-   ##
==========================================
- Coverage   87.58%   87.49%   -0.09%     
==========================================
  Files          16       17       +1     
  Lines        4220     4254      +34     
==========================================
+ Hits         3696     3722      +26     
- Misses        524      532       +8

Impacted Files	Coverage Δ
vtki/container.py	96.58% <100%> (+0.01%)	⬆️
vtki/utilities.py	93.42% <100%> (+0.05%)	⬆️
vtki/examples/examples.py	98.05% <100%> (ø)	⬆️
vtki/__init__.py	97.05% <100%> (+0.08%)	⬆️
vtki/pointset.py	91.17% <100%> (ø)	⬆️
vtki/readers.py	85.52% <85.52%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #100 into master will decrease coverage by 0.08%.
The diff coverage is 87.64%.

@@            Coverage Diff             @@
##           master     #100      +/-   ##
==========================================
- Coverage   87.56%   87.47%   -0.09%     
==========================================
  Files          16       17       +1     
  Lines        4222     4256      +34     
==========================================
+ Hits         3697     3723      +26     
- Misses        525      533       +8

Impacted Files	Coverage Δ
vtki/container.py	96.58% <100%> (+0.01%)	⬆️
vtki/utilities.py	93.42% <100%> (+0.05%)	⬆️
vtki/examples/examples.py	98.05% <100%> (ø)	⬆️
vtki/__init__.py	97.05% <100%> (+0.08%)	⬆️
vtki/pointset.py	91.17% <100%> (ø)	⬆️
vtki/readers.py	85.52% <85.52%> (ø)

---

Continue to review full report at Codecov.

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update ecc9356...aa3ad09. Read the comment docs.