#1325 add error messages

[valentinsulzer]

Description

Adds error message when the initial conditions are outside the bounds of the variable.

Fixes #1325

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 #1326 (8132da6) into develop (77e0767) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop    #1326   +/-   ##
========================================
  Coverage    98.12%   98.12%           
========================================
  Files          272      272           
  Lines        15431    15439    +8     
========================================
+ Hits         15142    15150    +8     
  Misses         289      289           

Impacted Files	Coverage Δ
pybamm/expression_tree/input_parameter.py	100.00% <ø> (ø)
pybamm/discretisations/discretisation.py	99.78% <100.00%> (+<0.01%)	⬆️
pybamm/solvers/casadi_algebraic_solver.py	98.71% <100.00%> (+0.03%)	⬆️

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[brosaplanella]

Look good, thanks Tino! Before merging we should add a line to the CHANGELOG.