Added Source Code Pro documentation.rst
Added Source Code Pro documentation.rst

Added a short blurb on Source Code Pro and how to make the glyphs show up.

Closes #460

dragon788/powerline,Luffin/powerline,DoctorJellyface/powerline,QuLogic/powerline,bezhermoso/powerline,russellb/powerline,magus424/powerline,S0lll0s/powerline,russellb/powerline,S0lll0s/powerline,bartvm/powerline,EricSB/powerline,areteix/powerline,magus424/powerline,junix/powerline,lukw00/powerline,firebitsbr/powerline,Luffin/powerline,cyrixhero/powerline,russellb/powerline,s0undt3ch/powerline,IvanAli/powerline,Liangjianghao/powerline,kenrachynski/powerline,bezhermoso/powerline,cyrixhero/powerline,xxxhycl2010/powerline,areteix/powerline,bartvm/powerline,EricSB/powerline,darac/powerline,wfscheper/powerline,seanfisk/powerline,seanfisk/powerline,xfumihiro/powerline,kenrachynski/powerline,S0lll0s/powerline,blindFS/powerline,xxxhycl2010/powerline,darac/powerline,prvnkumar/powerline,wfscheper/powerline,lukw00/powerline,lukw00/powerline,dragon788/powerline,wfscheper/powerline,seanfisk/powerline,QuLogic/powerline,blindFS/powerline,DoctorJellyface/powerline,IvanAli/powerline,bartvm/powerline,s0undt3ch/powerline,firebitsbr/powerline,prvnkumar/powerline,xxxhycl2010/powerline,QuLogic/powerline,junix/powerline,Liangjianghao/powerline,s0undt3ch/powerline,cyrixhero/powerline,firebitsbr/powerline,bezhermoso/powerline,xfumihiro/powerline,prvnkumar/powerline,magus424/powerline,DoctorJellyface/powerline,xfumihiro/powerline,areteix/powerline,darac/powerline,Liangjianghao/powerline,blindFS/powerline,dragon788/powerline,IvanAli/powerline,junix/powerline,Luffin/powerline,EricSB/powerline,kenrachynski/powerline