fix deprecated warnings on Julia 0.7

[bicycle1885]

No description provided.

[codecov-io]

Codecov Report

Merging #2 into master will not change coverage.
The diff coverage is 100%.

@@          Coverage Diff           @@
##           master      #2   +/-   ##
======================================
  Coverage    95.9%   95.9%           
======================================
  Files          14      14           
  Lines         513     513           
======================================
  Hits          492     492           
  Misses         21      21

Impacted Files	Coverage Δ
src/CodecBase.jl	100% <ø> (ø)	⬆️
src/buffer.jl	100% <100%> (ø)	⬆️
src/base64/codetable.jl	100% <100%> (ø)	⬆️
src/base16/codetable.jl	100% <100%> (ø)	⬆️
src/base32/codetable.jl	92% <100%> (ø)	⬆️

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