Prepare v0.0.2

[ebuchman]

• Fill in changelog for v0.0.2
• Add CONTRIBUTING.md
• Update all crate authors to generic Informal Systems
• Bump all crate versions to v0.0.2
• Use v0.15.0 of tendermint crates (instead of master)
• Rename relayer_modules to modules (closes Crate naming cosmos/ibc-rs#125)

[codecov-commenter]

Codecov Report

Merging #190 into master will increase coverage by 2.6%.
The diff coverage is 19.8%.

@@           Coverage Diff            @@
##           master    informalsystems/hermes#190     +/-   ##
========================================
+ Coverage    13.6%   16.2%   +2.6%     
========================================
  Files          69      59     -10     
  Lines        3752    3867    +115     
  Branches     1374    1491    +117     
========================================
+ Hits          513     630    +117     
+ Misses       2618    2483    -135     
- Partials      621     754    +133     

Impacted Files	Coverage Δ
modules/src/events.rs	0.0% <ø> (ø)
modules/src/ics02_client/client.rs	0.0% <0.0%> (ø)
modules/src/ics02_client/client_type.rs	47.6% <ø> (ø)
modules/src/ics03_connection/error.rs	25.0% <0.0%> (-8.4%)	⬇️
modules/src/ics03_connection/exported.rs	42.1% <0.0%> (-9.6%)	⬇️
modules/src/ics04_channel/error.rs	23.0% <0.0%> (-2.0%)	⬇️
modules/src/ics04_channel/packet.rs	0.0% <0.0%> (ø)
modules/src/ics07_tendermint/error.rs	33.3% <0.0%> (+33.3%)	⬆️
modules/src/ics07_tendermint/msgs/create_client.rs	0.0% <0.0%> (ø)
modules/src/ics23_commitment/mod.rs	0.0% <0.0%> (ø)
... and 70 more

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