glpk solver implementation, ready to start testing
glpk wrapper was added

the glpk wrapper and 2 unit tests were added:
 -  test_glpk_alone - checks if glpk produces the correct output for a
basic LP problem. the idea is to check that glpk alone is working well.
  - test_glpk_against_gurobi - solves the same problem with gurobi and
glpk and checks if the objective function values are the same.
code style according to pep8 + glpk instructions

the isntructions to install  python-glpk on Mac OS and linux were added
on the framed/misc folder.
the code previously changed was formatted according to pep8
Added glpk pickle test.
Forgot the changes in glpk_wrapper.py
Merge pull request #10 from cdanielmachado/marta-branch

Merging pull request from Marta to master branch