Add specialized unique/allunique methods for KnotVector

[sostock]

No description provided.

[codecov-commenter]

Codecov Report

Merging #4 into master will increase coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master       #4      +/-   ##
==========================================
+ Coverage   89.81%   89.85%   +0.04%     
==========================================
  Files           6        6              
  Lines         422      424       +2     
==========================================
+ Hits          379      381       +2     
  Misses         43       43              

Impacted Files	Coverage Δ
src/vectortypes.jl	100.00% <100.00%> (ø)

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