README: Fix build badge in README.md
README: Fix build badge in README.md

Fix build badge in README.md

PR-URL: #107 
Reviewed-By: Colin Ihrig <838f779c91673db29b8572ea3f54d191d3878ae2@gmail.com>
hhellyer/llnode,hhellyer/llnode,hhellyer/llnode,rnchamberlain/llnode,rnchamberlain/llnode,rnchamberlain/llnode,rnchamberlain/llnode,hhellyer/llnode