BUG: Addressed cmake config errors when TubeTK_USE_SLICER was set
ENH: Use TubeTK-specific var to track downloaded code, not Slicer_SOURCE_DIR
BUG: Reduce CMake version requirement until travis is upgraded.
Merge pull request #265 from aylward/CleanUpCMake

Clean up cmake
COMP: Bump JsonCpp to r276.

Add missing istream header for missing getline on Mac Clang build.
Merge pull request #266 from thewtex/jsoncpp-bump

COMP: Bump JsonCpp to r276.