Check for an existing project before building or creating directories

Previously ino would create a .build directory no matter where you ran it. I added a check to prevent the creation of directories if it is accidentally run in a non-project directory (a sub directory say). I've also made ino automatically create the lib directory if it doesn't exist. This way the build is more likely to succeed (if the project requires no libraries), or at least allow it to fail cleanly. Previously building without a lib directory would throw an exception about the directory not existing, now ino will just complain about the missing libraries.