Add Findfiles func to find files recursively (bitfield#36)

Merge pull request bitfield#44 from bitfield/execforeach

Add ExecForEach()

Merge pull request bitfield#43 from bitfield/concat_continue

Have Concat skip errors (fixes bitfield#26)

Merge pull request bitfield#42 from bitfield/better_exec

Fix Exec to handle quotes

Fix race condition on stdout in tests

Merge pull request bitfield#31 from bitfield/feature/path-filters

Add Basename and Dirname filters

Fix ordering

Merge pull request bitfield#19 from udithprabhu/feature/tail

Added Last filter to mimic tail command of shell

Merge pull request bitfield#2 from SmilingNavern/add-list-files

Add ListFiles function

Fix typo