fixed overwriting of roi
docs: Removed docs build artifacts from the git tree.
OpBlockedArrayCache: Request blocks in parallel.
Fixes ilastik/ilastik#613
tests: TestOpValueCache: Removed an incorrect assertion.
ValueRequest: Added block() function to mimic real request API.
tests: Skip OpInterpMissingData tests.
fillmissing: dependency check is now consistent
Merge pull request #112 from burgerdev/fillmissing_failing_tests

fillmissing: dependency check is now consistent
graph.py: Added the concept of graph "setup time", which clients can use to decide when to react to changes in the graph state.
timer: Added reset() method.
Memory manager: Use vmem.free to determine how much RAM is available, not vmem.available
(See ilastik/ilastik#699)
OpExportSlot: If the destination file exists, remove it before exporting.
Partial fix for ilastik/ilastik#643
utility: pathHelpers: Copied  functionality from ilastik/utility/pathHelpers, which is about to be deleted.
pathHelpers: getPathVariants returns None for relative path if the relative path doesn't exist.
Minor cleanup.
docs: Added PathComponents section.
stype: Commented out warnings about "deprecated" usage of "value slots".
Opened ilastik/ilastik#704, related to this.
Memory Manager: Init mem_usage to mem usage at app startup.
slot.value: Handle case where value is an iterable other than a list.
This fixes the particular issue observed in ilastik/lazyflow#76, which involved a "value slot" where the value is a dict.
This issue needs to be fixed more generally.  See also: ilastik/ilastik#704 and ilastik/ilastik#705
stype: Removed a warning from Opaque.writeIntoDestination().
Filed an issue concerning the warning that was removed, and added a comment explaining the issue.