mkdir init
add to makefile, basic mkdir functionality done
remove cat warning, update makefile
Fix test for cat, add mkdir test
Update readme, add success message at end of tests
move parent opt check, update tests
merge cat/test.rs
remove unneeded typing, swap cat and mkdir
update test dir paths into tmp dir
Merge pull request #55 from juszczakn/master

Implemented mkdir
mkdir: update for latest Rust

I'm doing this from my phone, but I assume that it's okay to do this directly seeing as I merged mkdir because it was easy to fix.