Fix: deprecated warnings with shoulda-matchers

Used assert_not_nil assigns instead of assert assign_to
Fix: deprecated warnings with shoulda-matchers

Used assert instead of respond_with_content_type
fix test fails in result
Merge pull request #43 from GhiGt/pr-1148

Fix test fails in results
Merge branch 'master' of github.com:benjaminvialle/Markus into DeprecatedTests
Merge branch 'DeprecatedTests' of github.com:benjaminvialle/Markus into DeprecatedTests
Merge branch 'master' of github.com:benjaminvialle/Markus into DeprecatedTests
fix problem in results tests
Merge pull request #44 from GhiGt/pr-1148

fix problem in results tests
Remove respond_with_content_type from assignments_controller_test.rb
Merge pull request #45 from danielstjules/DeprecatedTests

Remove respond_with_content_type from assignments_controller_test.rb
Merge pull request #1148 from benjaminvialle/DeprecatedTests

Fix: deprecated warnings in tests (shoulda-matchers)