Update README.md with some doc

README.md

@@ -1,2 +1,26 @@
 # fast-gpio
 Provides access to GPIOs by directly writing to the hw registers, implements sw PWM as well
+
+# usage
+
+    fast-gpio set-input <gpio>
+    fast-gpio set-output <gpio>
+    fast-gpio get-direction <gpio>
+    fast-gpio read <gpio>
+    fast-gpio set <gpio> <value: 0 or 1>
+    fast-gpio pwm <gpio> <freq in Hz> <duty cycle percentage>
+
+## verbose output modes
+
+Verbose flags available:
+
+* **-q** quite output
+* **-v** verbose output
+* **-u** ubus output
+* **-d** debug output
+
+Examples:
+
+    fast-gpio -q set-input 5
+    fast-gpio -u read 5
+    > {"cmd":"Read", "pin":12, "val":"1"}