Slightly clean up developer install doc
Slightly clean up developer install doc

Added a prerequisite section and removed the installation instructions for Leiningen
ashneo76/LightTable,fdserr/LightTable,brabadu/LightTable,EasonYi/LightTable,pkdevbox/LightTable,youprofit/LightTable,Bost/LightTable,youprofit/LightTable,kenny-evitt/LightTable,craftybones/LightTable,masptj/LightTable,hiredgunhouse/LightTable,EasonYi/LightTable,kolya-ay/LightTable,hiredgunhouse/LightTable,masptj/LightTable,ashneo76/LightTable,mrwizard82d1/LightTable,kausdev/LightTable,LightTable/LightTable,kenny-evitt/LightTable,fdserr/LightTable,EasonYi/LightTable,sbauer322/LightTable,masptj/LightTable,mpdatx/LightTable,Bost/LightTable,bruno-oliveira/LightTable,brabadu/LightTable,nagyistoce/LightTable,windyuuy/LightTable,Bost/LightTable,kausdev/LightTable,bruno-oliveira/LightTable,BenjaminVanRyseghem/LightTable,bruno-oliveira/LightTable,rundis/LightTable,brabadu/LightTable,craftybones/LightTable,kausdev/LightTable,sbauer322/LightTable,pkdevbox/LightTable,kolya-ay/LightTable,BenjaminVanRyseghem/LightTable,nagyistoce/LightTable,kolya-ay/LightTable,BenjaminVanRyseghem/LightTable,fdserr/LightTable,windyuuy/LightTable,0x90sled/LightTable,hiredgunhouse/LightTable,sbauer322/LightTable,mpdatx/LightTable,LightTable/LightTable,LightTable/LightTable,windyuuy/LightTable,kenny-evitt/LightTable,rundis/LightTable,mpdatx/LightTable,mrwizard82d1/LightTable,nagyistoce/LightTable,ashneo76/LightTable,mrwizard82d1/LightTable,pkdevbox/LightTable,rundis/LightTable,0x90sled/LightTable,craftybones/LightTable,0x90sled/LightTable,youprofit/LightTable