v0.0.8

- added support for sending multiple requests simultaneously (important
when using xowa_exec)
- socket : added support for  multiple clients connected to server
- fixed replacing ' --> '' in xowa_exec_async (it replacing only first
match)
- fixed injecting API immediately instead of waitng for DOM loaded
- added support for logging to files (sometimes useful when Firefox
hangs) - extensions.xowa_viewer.debug.log_path preference (it is path to
parent folder of logs)
- some code rafactoring