Added .navbar-toggleable-md class
Added .navbar-toggleable-md class

In Bootstrap 3, the menu collapsed on the -sm- breakpoint, I believe the equivalent of this breakpoint in Bootstrap 4 is actually the -md- breakpoint. The navbar currently has no option to collapse at the -md- breakpoint and I'd like to add this.
Hightrack/bootstrap,urbit/bootstrap,Scoutski/bootstrap,gijsbotje/bootstrap,9-chirno/chirno,tibo66/bootstrap,slavanga/bootstrap,m5o/bootstrap,afuno/bootstrap,joblocal/bootstrap,twbs/bootstrap,afuno/bootstrap,realcrowd/bootstrap,lipis/bootstrap,Hemphill/bootstrap-docs,lipis/bootstrap,n054/bootstrap,inway/bootstrap,copperdesign/bootstrap,davethegr8/bootstrap,igoynawamreh/bootstrap,fschumann1211/bootstrap,tibo66/bootstrap,joblocal/bootstrap,abvalentine/bootstrap,johnajacob/bootstrap,lemuelbarango/bootstrap,supergibbs/bootstrap,NCARB/bootstrap,supergibbs/bootstrap,TheFridayInstitute/bootstrap,david-schopf/bootstrap,Scoutski/bootstrap,frostbitten/bootstrap,gijsbotje/bootstrap,seanwu99/bootstrap,tibo66/bootstrap,TORO-IO/bootstrap,kvlsrg/bootstrap,blockstack/blockstack-bootstrap,NCARB/bootstrap,afuno/bootstrap,tibo66/bootstrap,blockstack/blockstack-bootstrap,SweetProcess/bootstrap,TheFridayInstitute/bootstrap,Hightrack/bootstrap,mpharrigan/bootstrap,urbit/bootstrap,gijsbotje/bootstrap,vitaligent/4,zalog/bootstrap,TORO-IO/bootstrap,Hightrack/bootstrap,Lyricalz/bootstrap,Lyricalz/bootstrap,inway/bootstrap,peterblazejewicz/bootstrap,abvalentine/bootstrap,bardiharborow/bootstrap,frostbitten/bootstrap,copperdesign/bootstrap,SweetProcess/bootstrap,hebbet/bootstrap,Delagen/bootstrap,vsn4ik/bootstrap,joblocal/bootstrap,janseliger/bootstrap,igoynawamreh/bootstrap,vsn4ik/bootstrap,wesamco/bootstrap-rtl,fschumann1211/bootstrap,johnajacob/bootstrap,afuno/bootstrap,JumpLinkNetwork/bootstrap-backward,GerHobbelt/bootstrap,andresgalante/bootstrap,xt0rted/bootstrap,JumpLinkNetwork/bootstrap-backward,Delagen/bootstrap,SweetProcess/bootstrap,davethegr8/bootstrap,bardiharborow/bootstrap,hebbet/bootstrap,m5o/bootstrap,realcrowd/bootstrap,yuyokk/bootstrap,bootstrapbrasil/bootstrap,lipis/bootstrap,coliff/bootstrap,janseliger/bootstrap,creativewebjp/bootstrap,bardiharborow/bootstrap,Hemphill/bootstrap-docs,jipexu/bootstrap,TheFridayInstitute/bootstrap,lemuelbarango/bootstrap,Scoutski/bootstrap,onenameio/rhythm-bootstrap,copperdesign/bootstrap,n054/bootstrap,lemuelbarango/bootstrap,edanbarak/bootstrap,TheFridayInstitute/bootstrap,Hemphill/bootstrap-docs,frostbitten/bootstrap,fschumann1211/bootstrap,bootstrapbrasil/bootstrap,luistelmocosta/bootstrap,frostbitten/bootstrap,peterblazejewicz/bootstrap,urbit/bootstrap,tomlutzenberger/bootstrap,edanbarak/bootstrap,IdanCo/bootstrap,xt0rted/bootstrap,vitaligent/4,slavanga/bootstrap,bardiharborow/bootstrap,creativewebjp/bootstrap,hebbet/bootstrap,wesamco/bootstrap-rtl,IdanCo/bootstrap,supergibbs/bootstrap,twbs/bootstrap,sealocal/bootstrap,9-chirno/chirno,n054/bootstrap,jipexu/bootstrap,janseliger/bootstrap,jipexu/bootstrap,johnajacob/bootstrap,nice-fungal/bootstrap,seanwu99/bootstrap,JumpLinkNetwork/bootstrap-backward,luistelmocosta/bootstrap,wesamco/bootstrap-rtl,wesamco/bootstrap-rtl,yuyokk/bootstrap,hebbet/bootstrap,kvlsrg/bootstrap,lemuelbarango/bootstrap,TORO-IO/bootstrap,mpharrigan/bootstrap,zalog/bootstrap,gijsbotje/bootstrap,creativewebjp/bootstrap,andresgalante/bootstrap,hellonewman81/bs4,edanbarak/bootstrap,stanwmusic/bootstrap,tagliala/bootstrap,kvlsrg/bootstrap,tjkohli/bootstrap,sealocal/bootstrap,supergibbs/bootstrap,JumpLinkNetwork/bootstrap-backward,Delagen/bootstrap,joblocal/bootstrap,yuyokk/bootstrap,seanwu99/bootstrap,realcrowd/bootstrap,realcrowd/bootstrap,Scoutski/bootstrap,SweetProcess/bootstrap,creativewebjp/bootstrap,luistelmocosta/bootstrap,igoynawamreh/bootstrap,GerHobbelt/bootstrap,Lyricalz/bootstrap,fschumann1211/bootstrap,blockstack/blockstack-bootstrap,tagliala/bootstrap,IdanCo/bootstrap,david-schopf/bootstrap,xt0rted/bootstrap,igoynawamreh/bootstrap,david-schopf/bootstrap,IdanCo/bootstrap,xt0rted/bootstrap,vitaligent/4,luistelmocosta/bootstrap,GerHobbelt/bootstrap,mpharrigan/bootstrap,9-chirno/chirno,n054/bootstrap,andresgalante/bootstrap,NCARB/bootstrap,davethegr8/bootstrap,lipis/bootstrap,stanwmusic/bootstrap,seanwu99/bootstrap,copperdesign/bootstrap,stanwmusic/bootstrap,coliff/bootstrap,vsn4ik/bootstrap,Delagen/bootstrap,davethegr8/bootstrap,janseliger/bootstrap,NCARB/bootstrap,tagliala/bootstrap,slavanga/bootstrap,hellonewman81/bs4,zalog/bootstrap,hellonewman81/bs4,inway/bootstrap,nice-fungal/bootstrap,sealocal/bootstrap,jipexu/bootstrap,peterblazejewicz/bootstrap,johnajacob/bootstrap,onenameio/rhythm-bootstrap,sealocal/bootstrap,bootstrapbrasil/bootstrap,vsn4ik/bootstrap,yuyokk/bootstrap,andresgalante/bootstrap,onenameio/rhythm-bootstrap,edanbarak/bootstrap,slavanga/bootstrap,stanwmusic/bootstrap,Hemphill/bootstrap-docs,tomlutzenberger/bootstrap,Lyricalz/bootstrap,abvalentine/bootstrap,tomlutzenberger/bootstrap,abvalentine/bootstrap,9-chirno/chirno,nice-fungal/bootstrap,tjkohli/bootstrap