bump elixir to 1.2.1 for travis
bump elixir to 1.2.1 for travis

problem: 
- there is a regression bug in elixir 1.2.0 when using assert macro in quoted code


solution: 
- https://github.com/elixir-lang/elixir/releases/tag/v1.2.1
- update to v.1.2.1
- [ExUnit] Ensure assert macros can be used from quoted code
- (at least I think that's the problem... not 100% sure)

nats-io/elixir-nats