Unbreak build status image in README.md (ultra minor pr)#787

AdamStormhardtGH wants to merge 1 commit intoFacepunch:masterFacepunch/Facepunch.Steamworks:masterfrom

AdamStormhardtGH:AdamStormhardtGH-patch-1-fix-build-status-imageAdamStormhardtGH/Facepunch.Steamworks:AdamStormhardtGH-patch-1-fix-build-status-imageCopy head branch name to clipboard