added field category in equipment

table equipment has new attribute “category” which shows the type of an
equipment (beamer, chair etc.)

reverted travis.yml
removed tabs in travis.yml
added schema.rb

migration was missing
Merge branch 'dev'
Merge remote-tracking branch 'remotes/origin/dev'
Merge remote-tracking branch 'remotes/origin/master' into feature/#12
#12 Added event view for rooms