Break main dotify binary apart into smaller pieces for easier testing

The plan is to have a build script that will put together all files into
a single executable again for easy inclusion in your own
dotfiles. Breaking dotify apart simply makes it easier to work with and
test.

src/lib/trim.sh

@@ -0,0 +1,13 @@
+# Trim leading and trailing whitespace.
+#
+# Example:
+#
+#   $ trim "  foo bar   "
+#   foo bar
+#
+trim() {
+  local string="$@"
+  string="${string#"${string%%[![:space:]]*}"}"
+  string="${string%"${string##*[![:space:]]}"}"
+  echo -n "$string"
+}