#833 manual implementation of levenshtein

[valentinsulzer]

Description

Removes dependency that was causing problems

Fixes #833

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

• New feature (non-breaking change which adds functionality)
• Optimization (back-end change that speeds up the code)
• Bug fix (non-breaking change which fixes an issue)

Key checklist:

• No style issues: $ flake8
• All tests pass: $ python run-tests.py --unit
• The documentation builds: $ cd docs and then $ make clean; make html

You can run all three at once, using $ python run-tests.py --quick.

Further checks:

• Code is commented, particularly in hard-to-understand areas
• Tests added that prove fix is effective or that feature works

[codecov]

Codecov Report

Merging #847 into master will increase coverage by 0.00%.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           master     #847    +/-   ##
========================================
  Coverage   98.24%   98.25%            
========================================
  Files         180      180            
  Lines       10254    10519   +265     
========================================
+ Hits        10074    10335   +261     
- Misses        180      184     +4     

Impacted Files	Coverage Δ
pybamm/util.py	97.34% <0.00%> (-2.66%)	⬇️
...odels/full_battery_models/lithium_ion/basic_dfn.py	100.00% <0.00%> (ø)	⬆️
...odels/full_battery_models/lithium_ion/basic_spm.py	100.00% <0.00%> (ø)	⬆️
pybamm/solvers/base_solver.py	99.44% <0.00%> (+0.05%)	⬆️

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[tlestang]

Looks good!