Update error output for python and dotnet scripts, and update makefile to requir…

…e dotnet framework 3.5

@@ -13,7 +13,7 @@ selftest:
 	bin/casperjs selftest
 
 compile-dotNET:
-	mcs -out:bin/casperjs.exe src/casperjs.cs
+	mcs -langversion:3 -out:bin/casperjs.exe src/casperjs.cs
 
 selftest-dotNET:
 	bin/casperjs.exe selftest

@@ -128,5 +128,5 @@ CASPER_COMMAND.extend(CASPER_ARGS)
 try:
     os.execvp(CASPER_COMMAND[0], CASPER_COMMAND)
 except OSError as err:
-    print('Fatal: %s; did you install phantomjs?' % err)
+    print('Fatal: %s; did you install %s?' % (err, ENGINE))
     sys.exit(1)

@@ -127,7 +127,6 @@ class casperjs {
             Environment.Exit(1);
         }
 
-
         foreach(string arg in args) {
             bool found = false;
             foreach(string native in ENGINE_NATIVE_ARGS) {
@@ -168,7 +167,7 @@ class casperjs {
                 Console.WriteLine(line);
             }
         } catch(Win32Exception e) {
-			Console.WriteLine(e.Message);
+            Console.WriteLine("Fatal: " + e.Message + "; did you install " + ENGINE + "?");
             Environment.Exit(1);
         }
     }