Test older versions of deps

[boyska]

When we assert that we depend on Fsdb <= 1.2, we should not only test against Fsdb==1.2.2, but also against older versions. In particular, I think we should pick older versions that used to be the most up to date in previous versions. Right now, this is:
Flask 0.11
passlib 1.6

For the future, each time we update dependencies we should add the previous versions in travis matrix