Merge pull request #184 from twsmith85/inputstream_int_return_fix

InputStream integer return fixes.

usbserial/src/main/java/com/felhr/usbserial/SerialInputStream.java

@@ -42,7 +42,7 @@ public class SerialInputStream extends InputStream
         int ret = device.syncRead(buffer, timeout);
         if(ret >= 0) {
             bufferSize = ret;
-            return buffer[pointer++];
+            return buffer[pointer++] & 0xff;
         }else {
             return -1;
         }
@@ -68,7 +68,7 @@ public class SerialInputStream extends InputStream
 
     private int checkFromBuffer(){
         if(bufferSize > 0 && pointer < bufferSize){
-            return buffer[pointer++];
+            return buffer[pointer++] & 0xff;
         }else{
             pointer = 0;
             bufferSize = -1;