Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

- Don't expand user home directory for variable names that simply have a
  HOME prefix;
- Support expansion of variables not followed by the path separator.

Also:

* Add check to .travis.yml that verifies that all code is gofmt-compliant
* Touch up some newlines

See #351

Fixes #261
Closes #265