Work around bug 1098470 by detecting manifest.* with getFeature (bug 1097424)

In Firefox OS 2.0 and 2.1 (possibly 2.2 if the bug isn't fixed soon),
hasFeature(manifest.*) will fail, but getFeature(manifest.*) will work.
add "Fireplace" heading to README
change screenshot in README (imgur → GitHub)
fix nav buttons for fxOS2.2 (bug 1095709)
reset the offset after switching between mkt/settings navbars
Merge pull request #824 from diox/workaround-has-feature-manifest-yulelog

Work around bug 1098470 by detecting manifest.* with getFeature (bug 1097424)
Merge pull request #825 from ngokevin/navbartweak23

fix nav buttons for fxOS2.2, reset offset switching between navbars
set href on nav switcher buttons (bug 1095709)
marketplace-core-modules v1.0.11
bump gulp/commonplace to switch api settings (bug 1099350)
Set the native-fxa class for native yulelog FxA (bug 1101751)
Merge pull request #826 from mstriemer/no-sign-out-yulelog-fxa-1101751

Hide Sign Out button with native yulelog FxA (bug 1101751)
WIP
reword comment
banner styling
remember dismissal, per spec
These tests are not necessary
Implement download button
better styling for close button
Implement applyUpdate