Update to julia 0.7

[davidanthoff]

Drops 0.6 support, and fixes the remaining deprecation warnings on 0.7.

[codecov[bot]]

Codecov Report

Merging #27 into master will increase coverage by 10.42%. The diff coverage is 100%.

@@             Coverage Diff             @@
##           master      #27       +/-   ##
===========================================
+ Coverage   87.22%   97.65%   +10.42%     
===========================================
  Files           3        3               
  Lines         415      298      -117     
===========================================
- Hits          362      291       -71     
+ Misses         53        7       -46

Impacted Files	Coverage Δ
src/FlatBuffers.jl	99.12% <100%> (+22.93%)	:arrow_up:
src/macros.jl	95.71% <100%> (+4.4%)	:arrow_up:
src/internals.jl	97.36% <0%> (+0.59%)	:arrow_up:

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[davidanthoff]

Thanks!