chore(Gruntfile): ensure bower command is run under node
chore(.gitignore): fix patterns

make patterns more strict so we don't accidentaly match stuff deeply
nested in the codebase.
feat(Grunt): add source maps to all min files

Generate source map files when build step is ran and adds source map
headers to all min files.

Source map url must be appended to the min file otherwise the line
offsets will be off.

Inspired by Ryan Seddon (PR #2858)

Closes #1714