Updating the escape characters to fix an issue with having a + in the branch name.

Since git allows for it the escape should not escape it since it then won't match the branch names correctly.
diff --git a/gitflow-common b/gitflow-common
index fb515de..4834cf1 100644
--- a/gitflow-common
+++ b/gitflow-common
@@ -45,7 +45,7 @@
 die() { warn "$@"; exit 1; }
 
 escape() {
-	echo "$1" | sed 's/\([\.\+\$\*]\)/\\\1/g'
+	echo "$1" | sed 's/\([\.\$\*]\)/\\\1/g'
 }
 
 # set logic