Fixing a typo and a spelling mistake on the comments of README.md

[smar152]

SIngle key -> Single key
Key Combenation -> Key Combination

[coveralls]

Pull Request Test Coverage Report for Build 192

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 81.406%

---

Totals
Change from base Build 191:	0.0%
Covered Lines:	193
Relevant Lines:	207

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💛 - Coveralls

[codecov-io]

Codecov Report

Merging #110 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #110   +/-   ##
=======================================
  Coverage   93.23%   93.23%           
=======================================
  Files           1        1           
  Lines         207      207           
=======================================
  Hits          193      193           
  Misses         14       14

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[jaywcjlove]

@smar152 thx!