[cti] Allow non-reactant orders for reaction

[imitrichev]

Resolves #317.
Adding new option nonreactant_orders that could be used in cti like this:

reaction("C8H18 + 12.5 O2 => 8 CO2 + 9 H2O", [4.6e11, 0.0, 30.0],
         order="C8H18:-0.25 CO:0.15", 
         options=['negative_orders', 'nonreactant_orders'])

In the example reaction order is specified for non-reactant CO.

[bryanwweber]

Thank you for adding this! Can you also add a test for this functionality? There is a class set up to test CTML conversion here: https://github.com/Cantera/cantera/blob/master/interfaces/cython/cantera/test/test_convert.py#L361
You can just add a new function to test the non-reactant orders

[speth]

I would assume that it would be easier to run the test suite on your own machine (scons test) and debug the issues there, although of course in the end the Travis build should also succeed.

The immediate cause of the failure is the lack of a colon at the end of your for statement.

I would also recommend not using assertEqual on floating point numbers. You can use assertNear instead.

[imitrichev]

Thank you for your suggestions! I've made the changes. Test test_reaction_orders now verifies conversion of negative and non-reactant reaction orders using reaction_orders.cti.

Please, look, if this is OK, when you have a time.