do not exit on not installed

lib/Compiler.js

@@ -35,9 +35,9 @@ function compileSolc(embark, contractFiles, cb) {
 
   const solc = shelljs.which('solc'); 
   if (!solc) {
-    logger.warn('solc is not installed on your machine');
+    logger.error('solc is not installed on your machine');
     logger.info('You can install it by following the instructions on: http://solidity.readthedocs.io/en/latest/installing-solidity.html');
-    process.exit();
+    return cb('Compiler not installed');
   }
   
   logger.info("compiling solidity contracts with command line solc...");

package.json

@@ -12,7 +12,7 @@
     "plugin",
     "contracts",
     "ethereum",
-	"embark"
+    "embark"
   ],
   "author": "Richard Ramos",
   "license": "ISC",