Merge branch 'feature/1.0.9'

Update rake version

Fix assign_sub and add tests

Fix specs and the Yaml loader

Refactor variable storage management

variable refactor

Convert placeholder to ops if needed

bug fix for grayscale jpg images

Add jpeg decode support

Merge branch 'master' of https://github.com/jedld/tensor_stream

Remove bundler version requirement

code cleanup

Add rounding to fix opencl tests (GPU returns a slightly different FP value)

remove binding.pry

Merge branch 'master' of https://github.com/jedld/tensor_stream