Update to sinatra 2.0.1

Although not a direct dependency, it's pulled in by Resque for
Active Job integration tests so we need to update because the
rack-protection gem has a security vulnerability[1].

[1]: https://nvd.nist.gov/vuln/detail/CVE-2018-7212

Gemfile.lock

@@ -321,7 +321,7 @@ GEM
     multi_json (1.12.2)
     multipart-post (2.0.0)
     mustache (1.0.5)
-    mustermann (1.0.0)
+    mustermann (1.0.2)
     mysql2 (0.4.9)
     mysql2 (0.4.9-x64-mingw32)
     mysql2 (0.4.9-x86-mingw32)
@@ -351,10 +351,10 @@ GEM
       selenium-webdriver
       thor
     racc (1.4.14)
-    rack (2.0.3)
+    rack (2.0.4)
     rack-cache (1.7.0)
       rack (>= 0.4)
-    rack-protection (2.0.0)
+    rack-protection (2.0.1)
       rack
     rack-test (0.8.0)
       rack (>= 1.0, < 3)
@@ -431,10 +431,10 @@ GEM
       faraday (~> 0.9)
       jwt (>= 1.5, < 3.0)
       multi_json (~> 1.10)
-    sinatra (2.0.0)
+    sinatra (2.0.1)
       mustermann (~> 1.0)
       rack (~> 2.0)
-      rack-protection (= 2.0.0)
+      rack-protection (= 2.0.1)
       tilt (~> 2.0)
     sneakers (2.5.0)
       bunny (~> 2.6.4)