GH-15: flag words as rare instead of bad in NeoVim

This change marks all words in all dictionaries as rare words so that
NeoVim highlights them as SpellRare instead of SpellBad.  This lets you
distinguish between wordy writing and normal misspellings, respectively.

In order for this to work, your NeoVim needs to be patched as follows:

  https://github.com/neovim/neovim/pull/2456

  https://groups.google.com/forum/#!topic/vim_dev/rPWOoR3ZgSA

See `:help spell-wordlist-format` for details about dictionary markings.

data-neovim/en/vague-time.dic

@@ -0,0 +1,187 @@
+# vague relative time references, where more precision could be used
+# http://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Words_to_watch
+/encoding=utf-8
+after hours/?
+after office hours/?
+after that/?
+after this/?
+after/?
+afterward/?
+age/?
+ahead of time/?
+already/?
+any day/?
+any hour/?
+any minute/?
+any month/?
+any second/?
+any week/?
+any year/?
+anytime/?
+as of this date/?
+at a later date/?
+at the buzzer/?
+at the end of the day/?
+at the last minute/?
+at the present time/?
+autumn/?
+back/?
+before long/?
+before now/?
+before then/?
+before you know it/?
+before/?
+beforehand/?
+behind schedule/?
+behind time/?
+behindhand/?
+belated/?
+belatedly/?
+by and by/?
+bygone/?
+currently/?
+dated/?
+day/?
+delayed/?
+directly/?
+earlier/?
+earliest/?
+early/?
+elapse/?
+elapsed/?
+ensue/?
+ensuing/?
+eon/?
+epoch/?
+era/?
+eventually/?
+exist/?
+existed/?
+existing/?
+fall/?
+following/?
+former/?
+formerly/?
+frequent/?
+frequently/?
+future/?
+generation/?
+has been/?
+have been/?
+having been/?
+immediate/?
+immediately/?
+imminent/?
+imminently/?
+impend/?
+impending/?
+impendingly/?
+in a bit/?
+in a flash/?
+in a little while/?
+in a minute/?
+in a moment/?
+in a second/?
+in a snap/?
+in a trice/?
+in a twinkle/?
+in a while/?
+in a wink/?
+in advance/?
+in an instant/?
+in due course/?
+in no time/?
+in the future/?
+in the near future/?
+in the past/?
+in the twinkling of an eye/?
+in time/?
+in two shakes/?
+instant/?
+instantly/?
+jiff/?
+jiffy/?
+just gone/?
+last day/?
+last hour/?
+last minute/?
+last month/?
+last second/?
+last week/?
+last year/?
+late/?
+lately/?
+later on/?
+later/?
+latest/?
+long past/?
+momentarily/?
+next day/?
+next hour/?
+next minute/?
+next month/?
+next second/?
+next week/?
+next year/?
+next/?
+night/?
+now/?
+once/?
+overdue/?
+overtime/?
+past/?
+period/?
+phase/?
+presently/?
+previously/?
+promptly/?
+punctual/?
+punctually/?
+quickly/?
+recent/?
+recent past/?
+recently/?
+remote future/?
+remote past/?
+running late/?
+shortly/?
+since/?
+soon/?
+sooner/?
+soonest/?
+span/?
+speedily/?
+spring/?
+subsequent/?
+subsequently/?
+succeeding/?
+suddenly/?
+summer/?
+tardily/?
+tardy/?
+then/?
+thereafter/?
+this week/?
+this year/?
+till all hours/?
+time/?
+to come/?
+to date/?
+today/?
+tomorrow/?
+traditionally/?
+untimely/?
+upcoming/?
+was/?
+when/?
+whenever/?
+will/?
+winter/?
+won't/?
+won’t/?
+would/?
+wouldn't/?
+wouldn’t/?
+years ago/?
+yesterday/?
+yesteryear/?