Remove links to pik from installation page

pik has been unmaintained for some time.
Remove links to pik from downloads page (de,en,it,ja,ko,pl)
Add uru to Ruby managers (en)
Add uru to Ruby managers (ko)
Specify packaged Ruby version on Arch Linux (en)
Merge pull request #917 from marocchino/ko-uru

Add uru to Ruby managers (ko)
add latest news post(ja): Rubyist Magazine 0049
Merge pull request #918 from muryoimpl/rubima-0049

add latest news post(ja): Rubyist Magazine 0049
Update list of excluded files
Updated Bulgarian translation
Merge pull request #912 from gmitrev/update-bulgarian-translation

Updated Bulgarian translation
Several small fixes on updated translation (bg)
Fix untranslated heading (bg)
Use relative link for subpage
Remove mention of fxri

RubyInstaller on Windows provides "Interactive Ruby".
Mention IRC channel (#ruby-lang) in link name
Adjust style of conference paragraph