Fix wget certificate issue

[zellux]

I'm seeing wget download issue due to https certificate. Fix the issue by skipping certificate check.

--2018-07-31 22:39:44--  https://shapenet.cs.stanford.edu/media/modelnet40_ply_hdf5_2048.zip
Resolving shapenet.cs.stanford.edu... 171.67.77.19
Connecting to shapenet.cs.stanford.edu|171.67.77.19|:443... connected.
ERROR: cannot verify shapenet.cs.stanford.edu's certificate, issued by ‘CN=InCommon RSA Server CA,OU=InCommon,O=Internet2,L=Ann Arbor,ST=MI,C=US’:
  Issued certificate has expired.
To connect to shapenet.cs.stanford.edu insecurely, use `--no-check-certificate'.