Check in the vendor directory

Travis seems to be having issues pulling deps, so we'll have to check in
the vendor directory and prevent the makefile from trying to regenerate
it normally.

vendor/github.com/hashicorp/golang-lru/doc.go

@@ -0,0 +1,21 @@
+// Package lru provides three different LRU caches of varying sophistication.
+//
+// Cache is a simple LRU cache. It is based on the
+// LRU implementation in groupcache:
+// https://github.com/golang/groupcache/tree/master/lru
+//
+// TwoQueueCache tracks frequently used and recently used entries separately.
+// This avoids a burst of accesses from taking out frequently used entries,
+// at the cost of about 2x computational overhead and some extra bookkeeping.
+//
+// ARCCache is an adaptive replacement cache. It tracks recent evictions as
+// well as recent usage in both the frequent and recent caches. Its
+// computational overhead is comparable to TwoQueueCache, but the memory
+// overhead is linear with the size of the cache.
+//
+// ARC has been patented by IBM, so do not use it if that is problematic for
+// your program.
+//
+// All caches in this package take locks while operating, and are therefore
+// thread-safe for consumers.
+package lru