improve tests, prevent errors in toSentence([]) and unquote(null)

[maciej-ka]

Functionality changes

toSentence

• Result of toSentence([]) is "" (previously it rised an error).
• Empty strings, null and undefined in array are ommited ... so toSentence([null, 'test', undefined]) will return 'test' (previously it was "null, test and undefined")

unquote

• Result of unqote(null) is "" (previously it rised an error).

Test improvements

camelizeze

• add uppercase string cases to test decapitalization
• remove similar cases of string with spaces

capitalize

• remove duplicate assertion

chop

• (formatting) remove space inside array

escapeRegExp

• add cases with null and undefined

lpad

• add case with length shorter than string

naturalCms

• add cases with numbers, empty strings, undefined and null

pad

• add case with length shorter than string

repeat

• add case with 0 and 1 repetitions

rpad

• add case with length shorter than string

splice

• add case with no substring
• add cases with null and undefined

toBoolean

• add cases with true, false, null and undefined

toSentence

• add cases with empty array, empty string, null and undefined

unquote

• add cases for empty string, null and undefined

[stoeffel]

@lokson Thx for your awesome work! Will review tonight.

[maciej-ka]

Ready with filter and omitted changes in dist - thanks for review.