Update changelog/ for new version of calens

We've reworked calens[1] a bit, the changelog/releases file is not
needed any more. Insteady, the release date is stored in the dir name
which contains the changelog entries.

[1] https://github.com/restic/calens

changelog/0.7.1_2017-07-22/issue-1055

@@ -0,0 +1,10 @@
+Enhancement: Create subdirs below `data/` for local/sftp backends
+
+The local and sftp backends now create the subdirs below `data/` on
+open/init. This way, restic makes sure that they always exist. This is
+connected to an issue for the sftp server:
+
+https://github.com/restic/rest-server/pull/11#issuecomment-309879710
+https://github.com/restic/restic/issues/1055
+https://github.com/restic/restic/pull/1077
+https://github.com/restic/restic/pull/1105

changelog/0.7.1_2017-07-22/issue-1067

@@ -0,0 +1,8 @@
+Enhancement: Allow loading credentials for s3 from IAM
+
+When no S3 credentials are specified in the environment variables, restic
+now tries to load credentials from an IAM instance profile when the s3
+backend is used.
+
+https://github.com/restic/restic/issues/1067
+https://github.com/restic/restic/pull/1086

changelog/0.7.1_2017-07-22/issue-1073

@@ -0,0 +1,8 @@
+Enhancement: Add `migrate` cmd to migrate from `s3legacy` to `default` layout
+
+The `migrate` command for chaning the `s3legacy` layout to the `default` layout
+for s3 backends has been improved: It can now be restarted with `restic migrate
+--force s3_layout` and automatically retries operations on error.
+
+https://github.com/restic/restic/issues/1073
+https://github.com/restic/restic/pull/1075

changelog/0.7.1_2017-07-22/issue-1081

@@ -0,0 +1,4 @@
+Enhancement: Clarify semantic for `--tasg` for the `forget` command
+
+https://github.com/restic/restic/issues/1081
+https://github.com/restic/restic/pull/1090

changelog/0.7.1_2017-07-22/plul-1080

@@ -0,0 +1,5 @@
+Enhancement: Ignore chmod() errors on filesystems which do not support it
+
+https://github.com/restic/restic/pull/1080
+https://github.com/restic/restic/pull/1112
+

changelog/0.7.1_2017-07-22/pull-1082

@@ -0,0 +1,3 @@
+Enhancement: Print stats on SIGINFO on Darwin and FreeBSD (ctrl+t)
+
+https://github.com/restic/restic/pull/1082

changelog/0.7.1_2017-07-22/pull-1115

@@ -0,0 +1,9 @@
+Bugfix: Fix `prune`, only include existing files in indexes
+
+A bug was found (and corrected) in the index rebuilding after prune, which led
+to indexes which include blobs that were not present in the repo any more.
+There were already checks in place which detected this situation and aborted
+with an error message. A new run of either `prune` or `rebuild-index` corrected
+the index files. This is now fixed and a test has been added to detect this.
+
+https://github.com/restic/restic/pull/1115