make_tarball: build from the current checkout, ignore Travis
Clean up typos and style in design doc

This includes:

- Fixing some typos and misspellings
- Being consistent with pronouns (she/he)
- Hyphenating "built-in" and "command-line" where appropriate
Cleanup fish tests a bit

Split `make test` into two targets `make test_low_level` and `make
test_fishscript`, primarily so fishscript tests can be rechecked quickly
after edits.

Reformat the test.fish file and update some of the code to be a little
more straightforward (e.g. `if not cmd` instead of `if cmd; else`).
Add a test harness for interactive behavior

Add a test harness that uses `expect` to drive Fish to test interactive
behavior.

Include some tests for `read`.
Disable fish_title on interactive tests

This was apparently what was interfering with the tests working on
Linux.

Tweak .travis.yml to install expect so the tests run on Linux.
Merge branch 'master' into pt-translation
Merge branch 'pt-translation' of github.com:riuri/fish-shell into pt-translation
translations: Update po with current master
Fixed typo