* Separate build integration tests; simplify test scripts
- Move build tests out of the regular Travis unit tests, add more smoke
test packages to build.
- Run all test scripts with bash -e, which fails on error.
- Factor coverage out into a Travis environment variable, so it's more
obvious from .travis.yml which tests contribute to coverage and which
don't.
- Factor dependency checking and much of the front-matter in tests
scripts into a setup.sh script, which is sourced by all the test
scripts. Extra cruft in each tests script now reduced to 2 lines at
the beginning.
- Ported old run-flake8-tests qa script to `spack flake8` command.
- New command does not modify files in the source tree
- Copies files to a temp stage modifies them there, and runs tests.
- Updated docs and `run-flake8-tests` script to call `spack flake8`.
* Warn user if flake8 can't find setuptools
* Add missing dependencies of flake8
* Updates to py-autopep8, make packages activateable
* Check for presence of setuptools for Sphinx too
* Fix bug in order of commands
