Change sphinx HTML theme to "nature".
Add .bak and .log files to gitignore.
Make inprovements to `nmapps.fs`.

* Add sphinx docstrings to most top-level elements in `nmapps.fs`.
* Fix `nmapps.fs.File.open` - problem with converting `nmapps.fs.Path`
  to string (the method never worked).
* Improve error handling in `nmapps.fs.File.open`, `nmapps.fs.File.read`
  and `nmapps.fs.File.write` - they throw an exception now by default,
  but can silently ignore it. They always log it using `logging` module
  though.
* Add `nmapps.fs.File.write`.
Add unit tests for .
Add basic monad implementation.
Fix some bugs in the `nmapps.injection` module, improve documentation.
Add new  module for formatted text output.
Add new  command to the . Add  module.
Add new bundle type - .
Merge branch 'feat/writers' into devel
Merge branch 'feat/monad' into devel