Issue 646 install

[valentinsulzer]

Description

Update Linux instructions with @jedgedrudd 's comments and add instructions for MacOS

Fixes #646
Fixes #673

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.

• 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

[valentinsulzer]

Accidentally created this branch from #674 so just going to merge into there

[codecov]

Codecov Report

Merging #680 into master will increase coverage by 0.04%.
The diff coverage is 98.63%.

@@            Coverage Diff             @@
##           master     #680      +/-   ##
==========================================
+ Coverage   98.14%   98.19%   +0.04%     
==========================================
  Files         180      181       +1     
  Lines        9987    10243     +256     
==========================================
+ Hits         9802    10058     +256     
  Misses        185      185

Impacted Files	Coverage Δ
pybamm/expression_tree/exceptions.py	100% <ø> (ø)	⬆️
pybamm/models/submodels/particle/base_particle.py	93.33% <ø> (-3.97%)	⬇️
...dels/submodels/particle/fast/base_fast_particle.py	100% <ø> (ø)	⬆️
pybamm/solvers/casadi_solver.py	100% <100%> (ø)	⬆️
...m/models/full_battery_models/base_battery_model.py	100% <100%> (ø)	⬆️
...bamm/parameters/standard_parameters_lithium_ion.py	100% <100%> (ø)	⬆️
...ernal_circuit/function_control_external_circuit.py	100% <100%> (ø)	⬆️
...els/submodels/particle/fast/fast_many_particles.py	100% <100%> (ø)	⬆️
...odels/full_battery_models/lithium_ion/basic_dfn.py	100% <100%> (ø)	⬆️
...odels/full_battery_models/lithium_ion/basic_spm.py	100% <100%> (ø)	⬆️
... and 18 more

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[valentinsulzer]

@tlestang is it still worth working on this or will you sort out Mac and Windows install using pip?

[martinjrobins]

These instructions look good to me. Just need to sort out the errors on the travis mac build...

[Scottmar93]

Looks good, will trust you that this works on macs :)