Update gems, git ignore test files (leading _)

.gitignore

@@ -1,3 +1,4 @@
 *.json
 data/cache/*
 !data/cache/.gitkeep
+_*.*

Gemfile

@@ -5,4 +5,5 @@ gem "launchy"
 gem "i18n"
 gem "rexml"
 gem "digest-crc"
+gem "ffi"
 # gem "async-websocket"

Gemfile.lock

@@ -10,7 +10,10 @@ GEM
       excon (~> 0.78.0)
       gosu (~> 1.1)
       gosu_more_drawables (~> 0.3)
+    digest-crc (0.6.4)
+      rake (>= 12.0.0, < 14.0.0)
     excon (0.78.1)
+    ffi (1.15.4-x64-mingw32)
     gosu (1.2.0)
     gosu_more_drawables (0.3.1)
     i18n (1.8.11)
@@ -18,6 +21,7 @@ GEM
     launchy (2.5.0)
       addressable (~> 2.7)
     public_suffix (4.0.6)
+    rake (13.0.6)
     rexml (3.2.5)
 
 PLATFORMS
@@ -26,6 +30,8 @@ PLATFORMS
 
 DEPENDENCIES
   cyberarm_engine
+  digest-crc
+  ffi
   i18n
   launchy
   rexml