Prevents username and password from being exposed in error tracebacks.

This is only safe as long as the username and password are never stored
in any new variables, but are only passed directly as

    browser.loginSEOpenID(live_testing.username, live_testing.password)

This change includes a test change because that test was leaking the
password's actual length.
Modifies README.md to add header for Jeremy's test branch.
Merge branch 'more-specific-test-message-prefixes' into test
Modifies Travis icon link in README to point to /branches page.
Merge branch 'more-travis-credentials' into test
Merge branch 'hiding-passwords' into test
Adds Stack Overflow Chat Sandbox (room 1) to the list of TEST_ROOMs.
Merge branch 'parameterized-test-rooms' into test

Conflicts:
	test/test_live_messages.py
Merge branch 'add-so-sandbox-test-room' into test
Fixing URL of test branch Travis icon in README.md 

[ci skip]
Adds MSE Chat Sandbox (room 651) to the list of TEST_ROOMs.
Merge branch 'add-mso-sandbox-test-room' into test
Merge branch 'issue-18-authentication-prompt' into test

Conflicts:
	test/test_live_messages.py
Merge branch 'master' into test
Merge branch 'nicer-test-message' into test

Conflicts:
	test/test_live_messages.py
Merge branch 'nicer-test-message' into test
Merge branch 'nicer-test-message' into test
Links Travis badge to build list instead of branch list

[no ci]
Merge branch 'sockets' into test
Merge branch 'sockets' into test