Fixed tpope's pathogen install step.

Previous instructions resulted in:

E117: Unknown function: pathogen#infect
E15: Invalid expression: pathogen#infect()
Press ENTER or type command to continue

New install instructions pulled from official 'vim-pathogen' README
gfortran now obtained through gcc package
Merge pull request #18 from cralor/patch-1

Fixes to pathogen & gfortran installation steps