1.1.1: get_linear_coefficients and fixes (#73)

* fix: support all numeric types

E.g. numpy and sympy

* chore: exception types

* fix: set problem attribute on objectives in new models

* fix: updated in Model __init__ breaks gurobi

* Get linear coefficients from solver (#72)

* feat: add get_linear_coefficients method

Abstract non-implemented method

* feat: implement glpk get_linear_coefficients method

* fix: typo

* feat: implement get_linear_coefficients in cplex

* feat: implement get_linear_coefficients in gurobi

* feat: implement get_linear_coefficients in scipy

* test: add tests for get_linear_coefficients

* test: more tests for get_linear_coefficients

* fix: flake8

* fix: missing arguments in test

* fix: make scipy consistent with other interfaces

the get_linear_coefficients and set_linear_coefficients methods now
raise an exception if the objective/constraint doesn’t belong to a model

* fix: objective.value should return None if not in model

* fix: get correct primal values from glpk MIPs

* test: add test for obj value without model

1.1.0: Small fixes (#68)

* fix: bug when changing variable names

Only update the _variables_to_constriants_mapping dict when new_name !=
old_name

* feat: allow infeasible primals to be retrieved

Only _round_primals_to_bounds if solution is optimal

* feat: add a tolerance option to scipy_interface

Default is set to 1e-9

1.0.5: Small fixes (#68)

* fix: bug when changing variable names

Only update the _variables_to_constriants_mapping dict when new_name !=
old_name

* feat: allow infeasible primals to be retrieved

Only _round_primals_to_bounds if solution is optimal

* feat: add a tolerance option to scipy_interface

Default is set to 1e-9

1.0.4: fix: bug when changing variable names (#63)

Only update the _variables_to_constriants_mapping dict when new_name !=
old_name

1.0.3: Fix cplex change var name (#62)

* fix: change variable name

* fix: move change to interface

Problem is not cplex-specific

* fix: bug in scipy_interface

Variables names were not updated in the bounds dictionary of the
Problem class

* test: add test in abstract test suite

1.0.2: fix: recursion problem in glpk_interface (#59)

_remove_variables would call self.variables for models with more than 350 variables.

1.0.1: Joss review (#55)

* chore: make example in README solver agnostic

And add a note on how to use a specific solver

* docs: add comments to README code

* Update requirements.txt

* docs: update README to reflect swiglpk as a dep.

swiglpk is a hard dependency now, so that 'pip install optlang' works out of the box.

* docs: update install instructions

Swiglpk is now a hard dependency so the installation instructions are updated accordingly.

* docs: update dependency versions in readme

* docs: update contributing guidelines

And add CONTRIBUTIONS.md file

* docs: update readme, paper and documentation

Add target audience to paper and docs/index
Add solver problem capabilities to readme
Move installation issue from readme to docs/installation

* test: remove libglp from travis.yml

* docs: highlight 'modeling language'

* docs: change paper title

* Some minor writing fixes (#57)

I made some minor writing fixes, to be adopted before acceptance in JOSS (https://github.com/openjournals/joss-reviews/issues/139)

1.0.0: docs: small formatting fix

Output from example was not shown in a code block, but just as indented text

0.6.4: fix: make model.Clone use json as default (#44)

* fix: make model.Clone use json as default

Using LP format as intermediate has problems on cross-solver clones.

* chore: add warning to clone with use_lp

* test: change clone test to use json

* fix: import warnings

* test: assert that cloned optimal value is the same

0.6.3: Fix recursion error (#42)

* fix: use sloppy keyword on Objective constructor

If sloppy, expressions will not be validated.

* chore: make is_Linear faster for canonical quadratic expressions

* fix: pep8