Added test for 503 when no upstream configured
Set 503 when no upstream is configured
Range request filtering for cache reads. Partial content from upstream marked as non-cacheable
Partial content is not cacheable
Merge pull request #89 from hamishforbes/master

Bug: ngx.var.args can be nil or an empty string
Reinstated background revalidation with a qless job
Revalidation job
initial tests for range requests
Merge branch 'master' of github.com:pintsized/ledge
Fixed range end offsets
Removed debug line
Test that cache misses with range requests go upstream, and trigger full background revalidation.
Added test for byte ranges outside entity length
Added tests for unsatisfiable and badly formatted ranges
Fixed handling of unsatisfiable byte ranges
Include tests for Cache-Control byte range response header
Include comma in header token pattern
Corrected byterange calculations and implemented multipart byteranges
Fixed multipart output format
Fixed range request filter to deal with ranges spanning partial chunks