* Catch web3 tx not found exception (API changed in versions > 5.0.0)
* Fix missing one_minus_ones elements
* Refresh the cache of preprocessed elements after the writing to file
  step is done. There was a line `pp_elements.init_mixins()` which looks
  like it was expected to do something similar but the method
  (`init_mixins()`) does not exist. Perhaps it can be implemented in the
  future.

Related to initc3#425

For the time being because it is sometimes difficult to understand why
the patch coverage is too low and this prevents moving forward with
merging a pull request which does not affect the overall coverage of the
project.

* Add documentation for asynchromix app.
* Remove extra whitespace in asynchromix contract