Bump required Bazel version to 2.1.0

Also bump bazlets to the latest master revision.

Change-Id: Ifa6a9ec659c79ff76dda49a6d17c1a2525682dd8

.bazelversion

diff --git a/.bazelversion b/.bazelversion
index 3eefcb9..7ec1d6d 100644
--- a/.bazelversion
+++ b/.bazelversion
@@ -1 +1 @@
-1.0.0
+2.1.0

WORKSPACE

diff --git a/WORKSPACE b/WORKSPACE
index 5770699..2b18bd9 100644
--- a/WORKSPACE
+++ b/WORKSPACE
@@ -4,7 +4,7 @@
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 load_bazlets(
-    commit = "97e83629a68dedda29125657a0a0a8cb21094de1",
+    commit = "f30a992da9fc855dce819875afb59f9dd6f860cd",
     #    local_path = "/home/<user>/projects/bazlets"
 )