ignore .git dir

For whatever stupid reason, the `.git` dir shows up on my NERDTree and
CtrlP results. Crazy right?
implement create_or_get_series controller

Ripped out this piece of logic to make SeriesHandler simpler.
implement create_or_get_chapter controller
chapter.series_name; better series update; tolerant bookmarks; thumb_url

- Chapter now has series_name
- Implement update_series() controller that can update all of its
  chapters with the latest series name if it has changed
- Bookmark APIs now reuse create_or_get_series/chapter(), so even if I
  delete all series/chapter records, the series/chapter bookmark APIs
  won't break.
- series_info() now returns thumb_url instead of thumbnailUrl for
  consistency.
better My Chapters route
show series name in chapter page title
add JSX comment to chapter_bookmarks