Update README.md

Readme.md

@@ -16,8 +16,10 @@ Plug a wire on GPIO 18, means Pin 12 of the GPIO header ([header P1](http://elin
 **rpitx** is the main software to transmit. It allows to transmit 
 	- from **IQ** files *.iq (could be generated by external software like gnuradio or by some few examples of modulations).
 	- from **Frequency/Time** files *.ft (generally used implement easily digital modes)  
-    
-    Usage:rpitx [-i File Input][-m ModeInput] [-f frequency output] [-s Samplerate] [-l] [-p ppm] [-h] 
+
+Usage:
+
+    rpitx [-i File Input][-m ModeInput] [-f frequency output] [-s Samplerate] [-l] [-p ppm] [-h] 
     -m            {IQ(FileInput is a Stereo Wav contains I on left Channel, Q on right channel)}
                   {IQFLOAT(FileInput is a Raw float interlaced I,Q)}
                   {RF(FileInput is a (double)Frequency,Time in nanoseconds}