fix requirements range error for travis test

[ccnifo]

Set correct parsable ranges on module requirements to pass Travis tests

[ccnifo]

@kreczko : I saw that stdlib 5.2.0 is available, maybe we can test it to enlarge the supported version range? Release notes for 5.0.0 say:

This is a major release which removes support for the Scientific 5 and Debian 7 OS, as well as a removal of the Stdlib::(Ipv4|IPv6|Ip_address) data types in favour of Stdlib::IP::*.

[kreczko]

sure, let's try it

[ccnifo]

I ran a pass with stdlib 5.2.0 on my CentOS7 cluster, no warning whatsoever on worker, master, or scheduler. Of course, one can have a different experience on a different cluster.

[ccnifo]

@kreczko and I've seen no mention of stdlib::ip in the module, so I guess we're OK? Would you prefer to merge as is or to include 5.x?

[ccnifo]

@kreczko : re-reading the release notes of stdlib 5.0.0 makes me thing it should run fine.
However, 1 or 2 module users testing it would be great!