lock bids validator version at 1.5.4

Author: Remi-Gau

.travis.yml

@@ -33,7 +33,7 @@ before_install:
   - travis_retry sudo apt-get -y install nodejs
   - travis_retry sudo apt-get -y install npm
   # Install BIDS-Validator
-  - sudo npm install -g bids-validator
+  - sudo npm install -g bids-validator@1.5.4
 
 install:
   # make octave file the JSONio submodule