text: Title: No (obvious) way to insert literal text that conflicts with an AutoKey "special key"
  Body: ## Classification:
  
  UI/Usability
  
  ## Reproducibility:
  
  Always
  
  ## Summary
  
  There's no obvious way to override the special handling of literal text in a `keyString`, so something as benign as trying to wrap clipboard text in `<code></code>` tags or using `keyboard.send_keys` with arbitrary clipboard text possibly containing tokens that AutoKey considers "special" will not work as expected.
  
  A secondary problem is that while the ability to parse raw keycodes within keyStrings is probably useful, it doesn't seem to be [terribly well-documented][api] (as in, you'd have to inspect [the source code][mediator] to discover it).
  
  ## Steps to Reproduce
  
  Create a script with the following contents and run it
  
  ```python
  keyboard.send_key("<code>test</code>")
  ```
  
  ## Expected Results
  
  Because keycode handling in `keyString`s appears to be undocumented, one would expect that the literal text `<code>test</code>` would show up in the active document / text area.
  
  ## Actual Results
  
  Nothing. You would never know anything was wrong (or right) without running `autokey-gtk -l` and seeing the following error message, due to the improper parsing of the keyString starting with `<code` (from `lib/iomediator_Key.py` [around line 67](../blob/master/lib/autokey/iomediator_Key.py#L67)):
  
  ```
  2017-11-27 21:01:03,548 DEBUG - interface - Send special key: ['<code>test</code>']
  2017-11-27 21:01:03,548 ERROR - interface - Error in X event loop thread
  Traceback (most recent call last):
    File "/home/user/.local/lib/python3.5/site-packages/autokey/interface.py", line 146, in __eventLoop
      method(*args)
    File "/home/user/.local/lib/python3.5/site-packages/autokey/interface.py", line 714, in __sendKey
      self.__sendKeyCode(self.__lookupKeyCode(keyName))
    File "/home/user/.local/lib/python3.5/site-packages/autokey/interface.py", line 961, in __lookupKeyCode
      return int(char[5:-1])
  ValueError: invalid literal for int() with base 10: '>test</code'
  ```
  
  ## Version
  
  AutoKey-Py3 version 0.93.10, installed via pip.
  
  Distro: elementaryOS Loki (Ubuntu 16.04 Xenial)
  
  ## Notes
  
  I respectfully suggest adding a `keyboard.send_keys_raw` or `keyboard.send_keys_unparsed` method, which does not parse the `keyString` for "special keys."
  
  ### Workaround
  
  ```python
  # split up part of "special key" across two calls to 'keyboard.send_key'
  keyboard.send_key("<")
  keyboard.send_key("code>test</code>")
  ```
  
  [api]: https://autokey.github.io/lib.scripting.Keyboard-class.html
  [mediator]: ../blob/master/lib/autokey/iomediator_Key.py