* Migrate to `unittest2`
why:
Global symbol overflow when running NIM 1.2 on Github ci suggests that
unit tests run sort of separately. The replacement library `unittest2`
provides that.
* Build ci dependencies
* Initial commit of io2 module
* Rename to io2.
Add createPath with permissions.
Add writeFile with permissions.
Add tests.
* Add test_io2 to all tests.
* Add posix permissions.
* Add toString procedure for set[Permission] and tests.
* Remove safeio.nim
* Add setPermissions procedures.
Fix writeFile() to change permissions.
Add more writeFile() tests.
* Change C ReadOnly/WriteOnly/ReadWrite to pair of Read/Write.
Add tests for openFile.
* File handles is no inherited by default, with option to turn on inheritance.
* Review comments fixes.
More tests.
* Fix x86 compilation problems.
* Rename toSet -> toPermissions.
* Avoid race condition on writeFile permissions.
Eugene Kabanov
tersec
Jordan Hrycaj