bump deps

test erlang 21, 22 (#77)

* test erlang/otp 21, use official rebar3

* update deps

* test erlang/otp 22

Merge pull request #49 from wk8/wk8/create_with_body

Adding an `erlastic_search:create_index/3` fun to allow creating an index with custom settings

Merge pull request #41 from wk8/wk8/index_changes

Some index changes:

automatic hex publishign and use git tag for version

travis build tags too

add automatic upload to hex of tags

updated for sinan usage as an option over rebar