Use struct literal for new cacheItem.
in_pipe -> in
Use struct literal for FileCache.
item_expired -> itemExpired
vaccuum -> vacuum
Range over tick
add Mutexes to filecache
remove snake names
Merge branch 'locking' into codereview

Conflicts:
	filecache.go
Fix typo in lock calls
Lock when getting items from cache.
Lock when deleting items.
Lock cache on accesses.
Add WaitGroup to cache
go fmt
Use default zero value for mutex.
Item should only be locked by item.
Pre-allocate stored file name list.
forcibly prevent callers from locking item
Use header handle to write headers.