add new test resources
create ChainedProcessor, make rubySassEngine thread-safe & add more unit tests for Less processors
add missing imports (pull request)

ws/1.6.x' into 1.6.x

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update cssImportFromComments regex (single line comment with @import statement update) & use static imports from org.junit.Assert
update test resources to pass with latest version of node coffee-script (1.6.2)
merge issue703
fix merge conflicts
update to coffee-script-1.6.2 & fix failing tests
merge issue709