fixing issue with @ symbol in _from

Author: mansona

lib/dependency-checker.js

@@ -119,6 +119,10 @@ class EmberCLIDependencyChecker {
         version = pkgContent.version || null;
         if (isTarGz(versionSpecified)) {
           version = pkgContent._from || unknownVersion;
+          if (version.includes('@')) {
+            // use the bit after the '@'
+            version = version.split('@')[1]
+          }
         }
       } catch(e) {
         // JSON parse error