Update readme file with version update info.

Readme.txt

@@ -1,13 +1,17 @@
 
-
 Version History
 ---------------
+0.7	-Bug fix: If detach() was called on a servo then subsequent calls to attach() would fail.
+          The detach() function now works properly.
+
+
 0.6 	-Added ability to easily select if this driver should use timer0 or
 	  timer1.
 	-Timer1 is now the default timer used. Used to be timer0.
 	-Made the timer init happen later to allow this driver to work when
 	  used with an attiny arduino library.
 	-Fixed bug where a 512 microsecond pulse would not be generated.
+
 
 0.5 	-Initial public release