Remove ascii check in obj file parsing

[ffreyer]

Fixes #101 by removing the ascii check. We're not indexing the string directly so I don't see why we couldn't allow unicode. The check has been there since the initial version (Julia ~0.4) of this file (as isvalid()) so it doesn't seem like it's been introduced to fix anything specific.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 74.69%. Comparing base (fd17a83) to head (0ddc863).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #102      +/-   ##
==========================================
- Coverage   74.72%   74.69%   -0.04%     
==========================================
  Files          10       10              
  Lines         736      735       -1     
==========================================
- Hits          550      549       -1     
  Misses        186      186              

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