Drop "sudo -E" when running "bundle install"

Get rid of erroneous "sudo -E" when running
"bundle install" as mentioned in README.md
as discussed in https://github.com/kmerz/graveio/pull/50
Merge pull request #52 from h5b/master

Drop "sudo -E" when running "bundle install"
Fix Typos in "public/bin/bury.rb".
Merge pull request #54 from h5b/bury

Fix Typos in "public/bin/bury.rb".
Generate model tag
Adding relations table for tags-posts
Merge branch 'tags' of github.com:basti1508/graveio into tags