Force searcher reload upon indexing

The IndexSearcher relying solely on the latest index file modification
time may fail when /index and a search endpoint are called in the same
seconds.

This fixes tests.test_metrics.MetricsTests.test_search_index which
failed on my machine.
Dev environment fixes

Update .gitignore and add tox to requirements-dev
Tiny improvement to utils.is_pattern

Avoid parsing the string multiple time by searching for all possible
pattern characters in a single pass.