Currently get error from Travis on this install step, and downgrading one
version appears to fix the problem.
"Could not find any downloads that satisfy the requirement pyOpenSSL>=0.13
(from requests[security])"
Cover Linux & OSX on the container infrastructure, but install
a later G++ to satisfy the tests' need for C++11.
Use a build matrix to include a variety of build variants:
- ASAN
- UBSAN
- LSAN
- Coverage via coveralls.io
test: invoke ASAN and coverage in Travis build
Also shift to use explicit build matrix
test: Use coveralls.io for coverage tracking
test: Add a build with UBSAN
Also expand and re-order the setting of environment variables
for easier modification.
test: Add LSAN build to Travis config
