Require f

This fixes an "Error: (void-function f-dirname)" error when starting up
without `f' being loaded.

Conflicts:
	flycheck.el
Link to the flycheck-d-unittest extension

Great work by @tom-tan.  Thank you for your efforts and support!
Release 0.14.1

Includes a hotfix for a missing dependency
Merge branch 'dependency-hotfix'

* dependency-hotfix:
  Release 0.14.1
  Link to the flycheck-d-unittest extension
  Require f