Revert "travis: full apt-get version"

This reverts commit 0509b392ecbf7d2d54a91740b72d4add0b91270a.
Revert "travis: using some apt-get instead of cpam"

This reverts commit c03740b7e7f5d4353baac35b326d005181804d76.
Revert "travis: adding an RRDs dependency"

This reverts commit 16fc319d880382d65724089f768bbf716968c720.
travis: adding rrds