python27Packages.youtube-dl: 2018.03.14 -> 2018.03.26.1

Semi-automatic update generated by https://github.com/ryantm/nix-update tools.

This update was made based on information from https://repology.org/metapackage/youtube-dl/versions.

These checks were done:

- built on NixOS
- ran `/nix/store/xh1vx2vp7syc711vijy1qs452xxkmk1n-youtube-dl-2018.03.26.1/bin/.youtube-dl-wrapped -h` got 0 exit code
- ran `/nix/store/xh1vx2vp7syc711vijy1qs452xxkmk1n-youtube-dl-2018.03.26.1/bin/.youtube-dl-wrapped --help` got 0 exit code
- ran `/nix/store/xh1vx2vp7syc711vijy1qs452xxkmk1n-youtube-dl-2018.03.26.1/bin/youtube-dl -h` got 0 exit code
- ran `/nix/store/xh1vx2vp7syc711vijy1qs452xxkmk1n-youtube-dl-2018.03.26.1/bin/youtube-dl --help` got 0 exit code
- found 2018.03.26.1 with grep in /nix/store/xh1vx2vp7syc711vijy1qs452xxkmk1n-youtube-dl-2018.03.26.1
- directory tree listing: https://gist.github.com/0697ddb269c38c62a33bd198ac505324