src/lib/hardware/vfio: get path to driver from environment variables
src/lib/hardware/vfio: get path to iommu_groups from environment variables
src/lib/hardware/vfio: function to check vfio availability
src/lib/hardware/pci: get path to pci devices from environment variables
src/lib/hardware/bus: use new functions to get path
src/apps/intel/intel_app: check vfio before test execution
src/apps/vhost/vhost_user: check vfio before test execution
src/apps/intel/intel_app: get pci id for test from environment variables
src/apps/vhost/vhost_user: get pci id for test from environment variables
src/core/memory: calculate size in bytes only if varialble is not null
src/core/memory: get path to hugepages files from environment variables
src/core/memory: get path to meminfo file from environment variable
src/Makefile: check exitcode of test
src/doc/hacking.md: environment variables info added
core/app.lua, lib/hardware/pci.lua, vfio.lua: variable naming style fixes
src/apps/intel/intel_app.lua: pci id default removed, check added
src/apps/vhost/vhost_user.lua: pci id default remived, checks added
src/doc/hacking.md: no defaults update, new variable added
.travis.yml: initial commit