Split lines prior to diffing

[briandealwis]

Fixes #271

$ out/container-diff diff --type=file --filename=/var/lib/dpkg/status.d/openjdk remote://gcr.io/distroless/java@sha256:b430543bea1d8326e767058bdab3a2482ea45f59d7af5c5c61334cd29ede88a1 remote://gcr.io/distroless/java@sha256:bb1c9179c2263733f235291998cb849d52fb730743125420cf4f97a362d6a6dd
[...]
-----Diff of /var/lib/dpkg/status.d/openjdk-----


--- gcr.io/distroless/java@sha256:b430543bea1d8326e767058bdab3a2482ea45f59d7af5c5c61334cd29ede88a1
+++ gcr.io/distroless/java@sha256:bb1c9179c2263733f235291998cb849d52fb730743125420cf4f97a362d6a6dd
@@ -3 +3 @@
-Version: 8u171-b11-1~deb9u1
+Version: 8u181-b13-1~deb9u1
@@ -6 +6 @@
-Installed-Size: 97311
+Installed-Size: 97352

[aaron-prindle]

LGTM! Thanks!