Structs for Wire Protocol HTLCs and Commitments

* Structs and wire messages for HTLCs
* Wire protocol for a state machine with no blocking(!!!)
  (I will write the state machine)
  TL;DR: Can do multiple HTLC modifications in-flight, dead simple wire
  protocol. Both sides can update their Commitments unliaterally without
  waiting for the other party's signature. Will have basic/preliminary
  notes in the README
* Added **swp to .gitignore because of vim annoyances

.gitignore

@@ -34,3 +34,6 @@ cmd/lncli/lncli
 cmd/lnshell/lnshell
 
 test_wal/*
+
+# vim
+**.swp