add test that checks not expressions in declaration are not evaluated

see https://github.com/sass/libsass/pull/349
Merge pull request #95 from nsams/not-expr-in-declaration

add test that checks not expressions in declaration are not evaluated
Revert "Activate specs for issue 368"
Merge pull request #141 from sass/revert-140-wip/activate-issue-368

Revert "Activate specs for issue 368"
Activate specs for issue 349
Merge pull request #142 from xzyfer/wip/activate-issue-349

Activate specs for issue 349
Add specs for issue 660
Merge pull request #143 from xzyfer/wip/issue_660

Add specs for issue 660
Add specs for issue 623
Merge pull request #144 from xzyfer/wip/activate-issue-623

Add specs for issue 623
Revert "Add specs for issue 623"
Merge pull request #145 from sass/revert-144-wip/activate-issue-623

Disable specs for issue 623
Add spec test for issue #666 (convert angles)

Also add similar test spec for length units.
Merge pull request #146 from mgreter/master

Add spec test for issue #666 (convert angles)