Newcomers_Guide.rst: Change newcomers' issues link
Newcomers_Guide.rst: Change newcomers' issues link

Changes the link to coala.io/new
because the organization was renamed,
the old link did not reflect the new changes,
so it would lead to an empty page.

Fixes https://github.com/coala/documentation/issues/110

virresh/documentation,coala/documentation,rhemon/documentation,kshitijkg01/documentation,Asnelchristian/documentation,lusy/coala-documentation,Warewolf96/documentation,Akki356/documentation,coala/documentation,Kevchen/documentation,AnishHota/documentation,tamj0rd2/documentation,abhishekbundela/documentation,cristinabuciu/documentation,coala/documentation