add-coverage-to-gitignore (patch 1 of 1)

'git apply --summary --stat --apply --verbose' output was:

 .gitignore |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

For original context, see http://www.postgresql.org/message-id/CAFcNs+oVegX_Gw98ejiteH0k8qJ0svhm3WzLSybrsMSv0FkAKg@mail.gmail.com
Adding travis.yml