Add '.cache' to .gitignore. (#155)

diff --git a/.gitignore b/.gitignore
index 38fa1a7..e402d07 100644
--- a/.gitignore
+++ b/.gitignore
@@ -28,4 +28,4 @@
 *.kdev4
 DartConfiguration.tcl
 bazel-*
-
+.cache