Bundle static copy of Unicode emoji data with package

[bsolomon1124]

...at install time, rather than requiring a runtime download
of the codes from unicode.org.

SemVer MAJOR:

• Drop support for Python 2 and Python 3.5
• The demoji package now bundles emoji data that is distributed with the
  package at install time, rather than requiring a download of the codes
  from the unicode.org site at runtime (closes Bundle emojis in package #23)
• As a result of the above change, the following functions are removed
  from the demoji API:
  • download_codes()
  • parse_unicode_sequence()
  • parse_unicode_range()
  • stream_unicodeorg_emojifile()

SemVer MINOR:

• The demoji.DIRECTORY and demoji.CACHEPATH attributes are deprecated
  due to no longer being functionally in used by the package. Accessing them
  will warn with a FutureWarning, and these attributes may be removed
  completely in a future release
• demoji can now be installed with optional ujson support for faster loading
  of emoji data from file (versus the standard library's json, which is the
  default); use python -m pip install demoji[ujson]
• The dependencies requests and colorama have been removed completely
• importlib_resources (a backport module) is now required for Python < 3.7
• The EMOJI_VERSION attribute, newly added to demoji, is a str denoting
  the Unicode database version in use

SemVer PATCH:

• Fix a typo in demoji.__all__ to properly include demoji.findall_list()
• Internal change: Functions that call set_emoji_pattern() are now decorated
  with a @cache_setter to set the cache
• Some unit tests have been removed to update the change in behavior from
  downloading codes to bundling codes with install

Closes #28
Closes #27
Closes #23
Closes #11
Closes #4