STY: remove dead code.
MAINT: move enstaller tests into enstaller.tests
FEAT: add optional argv argument to enstaller.main.
REF: put indexed_repo-related tests into enstaller.indexed_repo.
TST: add a simple http store test that does not mock network.
MAINT: tweak tox config to erase previous coverage runs.
TST: add high-level test for enstaller update mechanism.
TST: don't include enstaller.verlib in coverage.

This is bundled code.
MAINT: add branch coverage tox env.
BUG: fix repo name tests when prefix is not normalized.
MAINT: fix travis-ci configuration.
STY: fix missing blank line.
DOC: clarify the choice of low/high versions in enstaller update tests.
Merge branch 'test_enstaller'
REF: refactor enpkg tests to remove redundant dummy* stores.
REF: move store tests into enstaller.store.
TST: add tests for exit_if_sudo_on_venv and other utils functions.
TST: add simple tests for LocalIndexedStore.
DOC: document the AbstractStore API.
TST: add some basic tests for JoinedStore.