Nil passed to clean_mixed_content will error in view

Cast value to string will prevent display error in search results
when value is nil. This comes up in the context of events as those
do not have a title or display string currently.
Merge pull request #106 from mark-cooper/events_related_fix

Nil passed to clean_mixed_content will error in view
test for Event in search bug
Add a small clarification for copying config.rb across multiple releases
fixes EAD to PDF issues with no components
updating README about java 8
Merge pull request #107 from marktriggs/upgrade-doc-clarification

Add a small clarification for copying config.rb across multiple releases
import export fixes for containers, finding_aid_filing_title, and lists not in notes
Merge branch 'master' of https://github.com/archivesspace/archivesspace