glpk solver uses izip in create_problem
glpk solver uses izip in create_problem

speeds up problem_creation by 9% while using less memory

jerkos/cobrapy,zakandrewking/cobrapy,jeicher/cobrapy,aebrahim/cobrapy,jerkos/cobrapy,zakandrewking/cobrapy,aebrahim/cobrapy,JuBra/cobrapy,jeicher/cobrapy,JuBra/cobrapy