Release 2.6.7

• If the first candidate is exactly the same as the typed string
  prefer longer candidates (Extends inline completions automatically)
• Move README to README.md and use some markdown to make it look better on github
• When showing similar emoji in the lookup table, show the list of keywords
  which matched only when debugging is on
• Update emoji annotations from CLDR
• More unittests, restructure test files, move some doctests to unittests
• Add a utility class KeyvalsToKeycodes to find ibus key codes
  instead of hardcoding them
• Add ceb to CLDR_ANNOTATION_FILES