Ensures order of constants in the code generator tests.
Ensures order of constants in the code generator tests.

Fixes issue #162.

oliverlee/pydy,Shekharrajak/pydy,oliverlee/pydy,jcrist/pydy,skidzo/pydy,jcrist/pydy,skidzo/pydy,jcrist/pydy,skidzo/pydy,jcrist/pydy,skidzo/pydy,oliverlee/pydy,Shekharrajak/pydy,Shekharrajak/pydy,jcrist/pydy,jcrist/pydy,Shekharrajak/pydy,jcrist/pydy