Issue 191 python3.5

[martinjrobins]

Description

Fixes #191

Key issue was that for python 3.5 (and lower) the dict class is unordered, so python is free to reorder things as it likes. We were assuming in a few places that the order of our dicts was fixed, so this was throwing errors.

other issues were to do with scikits.odes:

1. there was a strange cython bug regarding multiple imports, which occured when we tried to import ida many times
2. need to make sure travis has the correct version of the python header files
3. scikits.odes actually depends on numpy v 1.16, so bumped this version in pybamm's requirements

Type of change

Please delete options that are not relevant.

• 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
• Any dependent changes have been merged and published in downstream modules

[codecov]

Codecov Report

Merging #364 into master will increase coverage by 0.3%.
The diff coverage is 97.5%.

@@            Coverage Diff            @@
##           master     #364     +/-   ##
=========================================
+ Coverage   97.32%   97.62%   +0.3%     
=========================================
  Files          60       60             
  Lines        3921     4549    +628     
=========================================
+ Hits         3816     4441    +625     
- Misses        105      108      +3

Impacted Files	Coverage Δ
pybamm/parameters/parameter_values.py	99.33% <100%> (+1.04%)	⬆️
pybamm/discretisations/discretisation.py	99.28% <100%> (+0.35%)	⬆️
pybamm/solvers/scikits_dae_solver.py	95.45% <100%> (+1.33%)	⬆️
pybamm/meshes/submeshes.py	95.45% <80%> (-4.55%)	⬇️
pybamm/models/submodels/particle.py	94% <0%> (-1.24%)	⬇️
pybamm/spatial_methods/finite_volume.py	98.03% <0%> (-0.92%)	⬇️
pybamm/models/submodels/electrolyte_current.py	98.7% <0%> (-0.21%)	⬇️
pybamm/processed_variable.py	100% <0%> (ø)	⬆️
pybamm/models/submodels/electrode.py	100% <0%> (ø)	⬆️
pybamm/models/base_models.py	98.37% <0%> (+0.17%)	⬆️
... and 7 more

---

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 f6a7314...f8b9b60. Read the comment docs.

[valentinsulzer]

Looks great as is, thanks @martinjrobins . Was there anything else that needed to be done from #191? (rewriting docs?)

[martinjrobins]

Was there anything else that needed to be done from #191? (rewriting docs?)

I don't think so, the README already states that we support Python 3.5+, so nothing to change there