Fix modifications of settings & saving (#157)

Fix modifications of settings & saving (#157)

Fix crash on active view being a HtmlSheet (#155)

Fix UnicodeDecodeError on non-UTF-8 files (#151)

Co-authored-by: Rafal Chlodnicki <rchl2k@gmail.com>

Add settings schema for LSP-json (#149)

Fix crash when "syntax_ignore" option is customized (#143)

Clean up settings handling (#140)

- Use sublime_lib.NamedSettingsDict to handle settings
- apart from `trailing_spaces_highlight_color` which has special handling,
  get all options directly from settings so that they are always up-to-date
  with user preferences. Previously settings were only read on init.
- remove `trailing_spaces_` prefixes from settings. Settings with prefixes
   are still respected for backward-compatibility.

Run async versions of all listeners (#139)

Matching trailing space was done synchronously on file modification,
activation, and cursor movements but asynchronously after that from
an interval. Now we do matching asynchronously in all cases.

Ignore widgets (#138)

Resolves #84

ST2 release