Added gitignore which lets git ignore build files.

20160425/.gitignore

+.chardev-1.ko.cmd
+.chardev-1.mod.o.cmd
+.chardev-1.o.cmd
+.chardev-1write.ko.cmd
+.chardev-1write.mod.o.cmd
+.chardev-1write.o.cmd
+.hellomod-1.ko.cmd
+.hellomod-1.mod.o.cmd
+.hellomod-1.o.cmd
+.tmp_versions/
+Module.symvers
+chardev-1.ko
+chardev-1.mod.c
+chardev-1.mod.o
+chardev-1.o
+chardev-1write.ko
+chardev-1write.mod.c
+chardev-1write.mod.o
+chardev-1write.o
+hellomod-1.ko
+hellomod-1.mod.c
+hellomod-1.mod.o
+hellomod-1.o
+modules.order
+