Lowercase %i stands for
Non-interpolated Array of symbols, separated by whitespace (after Ruby 2.0)
In addition, uppercase %I means
Interpolated Array of symbols, separated by whitespace (after Ruby 2.0)
Example of difference regarding interpolation:
2.4.2 :001 > a = 1
2.4.2 :002 > %i{one two #{a}+three} # Interpolation is ignored
=> [:one, :two, :"\#{a}+three"]
2.4.2 :003 > %I{one two #{a}+three} # Interpolation works
=> [:one, :two, :"1+three"]
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