changes for precompilation in Julia 1.0

[codecov[bot]]

Codecov Report

Merging #28 into master will not change coverage. The diff coverage is 100%.

@@           Coverage Diff           @@
##           master      #28   +/-   ##
=======================================
  Coverage   97.46%   97.46%           
=======================================
  Files           9        9           
  Lines         513      513           
=======================================
  Hits          500      500           
  Misses         13       13

Impacted Files	Coverage Δ
src/meanshift.jl	100% <ø> (ø)	:arrow_up:
src/region_growing.jl	100% <100%> (ø)	:arrow_up:

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[timholy]

Thanks!