Updated to make use of the new pcp::cache functions currently on the pcp-pmda-cpp project's cache branch; will merge to trunk after more pcp-pmda-cpp testing.
Extracted the PMDA++ version in the Travis CI config (not sure this is valid; if not, I'll have to use 'env').
Corrected the download URL.
A small code simplification.
More Travis CI config.
Download links are slightly different between v1.2.3 and 'master'.
Lacking a dash.