Reorder pip arguments in installation documentation
Reorder pip arguments in installation documentation

`--editable`/`-e` pip argument is accepting an argument, not specifying the
action.

cyrixhero/powerline,EricSB/powerline,DoctorJellyface/powerline,seanfisk/powerline,darac/powerline,IvanAli/powerline,IvanAli/powerline,bezhermoso/powerline,Liangjianghao/powerline,bezhermoso/powerline,wfscheper/powerline,seanfisk/powerline,bartvm/powerline,cyrixhero/powerline,dragon788/powerline,Liangjianghao/powerline,lukw00/powerline,prvnkumar/powerline,xfumihiro/powerline,xfumihiro/powerline,DoctorJellyface/powerline,kenrachynski/powerline,lukw00/powerline,prvnkumar/powerline,DoctorJellyface/powerline,dragon788/powerline,bezhermoso/powerline,areteix/powerline,junix/powerline,QuLogic/powerline,prvnkumar/powerline,russellb/powerline,darac/powerline,kenrachynski/powerline,Liangjianghao/powerline,blindFS/powerline,QuLogic/powerline,blindFS/powerline,xxxhycl2010/powerline,kenrachynski/powerline,xxxhycl2010/powerline,darac/powerline,s0undt3ch/powerline,areteix/powerline,bartvm/powerline,Luffin/powerline,areteix/powerline,seanfisk/powerline,s0undt3ch/powerline,Luffin/powerline,cyrixhero/powerline,junix/powerline,junix/powerline,Luffin/powerline,S0lll0s/powerline,EricSB/powerline,bartvm/powerline,QuLogic/powerline,russellb/powerline,lukw00/powerline,S0lll0s/powerline,wfscheper/powerline,xfumihiro/powerline,blindFS/powerline,s0undt3ch/powerline,xxxhycl2010/powerline,S0lll0s/powerline,IvanAli/powerline,wfscheper/powerline,russellb/powerline,EricSB/powerline,dragon788/powerline