Add HN domain for posts without an external link
Merge pull request #6 from TimPetricola/master

Add HN domain for posts without an external link. 
Added action to open comments link of post

Press 'D' to launch a browser tab for HN comments link of post

@ciaranarcher also tidied up tests, and split header with commands into two lines.
Bump to 0.0.4
Merge remote-tracking branch 'upstream/master' into scrollable
Updated magic number because the size of the header changed.
Scrolling logic is complete.
Changed set_size to set_sizegit add ui.rb because that seems to be the convention.