add support for writing Normed{T,N} data

[chrstphrbrns]

Fix for #181

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 95.83333% with 2 lines in your changes missing coverage. Please review.

Project coverage is 92.86%. Comparing base (8cd9370) to head (3420b60).

Files with missing lines	Patch %	Lines
src/ifds.jl	87.50%	1 Missing ⚠️
src/types/dense.jl	97.50%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #182      +/-   ##
==========================================
+ Coverage   92.36%   92.86%   +0.50%     
==========================================
  Files          14       14              
  Lines        1153     1192      +39     
==========================================
+ Hits         1065     1107      +42     
+ Misses         88       85       -3     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[tlnagy]

Thanks @chrstphrbrns, just a minor point about the function name and I'll merge this.