css: make count column 1em wider

This allows for up to 99,999 objects before the line wraps. An
alternative solution would be to let the column resize itself, but I
didn't do that since it would make it differnet from page to page.
Merge pull request #51 from mgeisler/checkboxes

Add a column of checkboxes
Merge pull request #52 from mgeisler/column-sizing

css: make count column 1em wider
travis: make PATH a global (non-matrix) env variable

This means that PATH is not used to define a build matrix. Travis can
use (combinations of) environment variables to define a build matrix.
Here we just want to set the value globally for the build.