Added a section on --type_cache_ttl.
Added a section on --type_cache_ttl.

jacobsa/timeutil,jacobsa/ratelimit,BanzaiMan/gcsfuse,GoogleCloudPlatform/gcsfuse,kahing/gcsfuse,GoogleCloudPlatform/gcsfuse,BanzaiMan/gcsfuse,mbrukman/gcsfuse,GoogleCloudPlatform/gcsfuse