Migrate changelog from wiki into source tree

CHANGELOG.md

@@ -0,0 +1,49 @@
+Note: this changelog only lists feature additions, not bugfixes. For details on
+those, see the Git history.
+
+* v1.19
+    * Add `mode:` option for `create`
+    * Add `exclude:` option for `link`
+* v1.18
+    * Add `--only` and `--except` flags
+    * Add support to run with `python -m dotbot`
+    * Add `--force-color` option
+* v1.17
+    * Add `canonicalize-path:` option for `link`
+* v1.16
+    * Add `create` plugin
+* v1.15
+    * Add `quiet:` option for `shell`
+* v1.14
+    * Add `if:` option for `link`
+* v1.13
+    * Add `--no-color` flag
+* v1.12
+    * Add globbing support to `link`
+* v1.11
+    * Add force option to `clean` to remove all broken symlinks
+* v1.10
+    * Update `link` to support shorthand syntax for links
+* v1.9
+    * Add support for default options for commands
+* v1.8
+    * Update `link` to be able to create relative links
+* v1.7
+    * Add support for plugins
+* v1.6
+    * Update `link` to expand environment variables in paths
+* v1.5
+    * Update `link` to be able to automatically overwrite broken symlinks
+* v1.4
+    * Update `shell` to allow for selectively enabling/disabling stdin, stdout,
+      and stderr
+* v1.3
+    * Add support for YAML format configs
+* v1.2
+    * Update `link` to be able to force create links (deleting things that were
+      previously there)
+    * Update `link` to be able to create parent directories
+* v1.1
+    * Update `clean` to remove old broken symlinks
+* v1.0
+    * Initial commit