Cleans up code

[vsreekanti]

Amongst other things:

• Resolves #31.
• Aliases commonly used collection types with the using keyword in include/types.hpp.
• Consolidates key statistics and replication factor information into KeyMetadata.
• Cleans up implementation of *Thread classes.
• Changes a variety of variable names for clarity.

This is dependent on #65.

[codecov[bot]]

Codecov Report

Merging #66 into master will decrease coverage by 0.47%. The diff coverage is 62.9%.

@@            Coverage Diff            @@
##           master     #66      +/-   ##
=========================================
- Coverage   66.88%   66.4%   -0.48%     
=========================================
  Files          48      48              
  Lines        1531    1542      +11     
=========================================
  Hits         1024    1024              
- Misses        507     518      +11

Impacted Files	Coverage Δ
include/zmq/zmq_util.hpp	100% <ø> (ø)	:arrow_up:
kvs/tests/mock/mock_utils.hpp	100% <ø> (ø)	:arrow_up:
kvs/include/hash_ring.hpp	91.3% <ø> (ø)	:arrow_up:
kvs/tests/mock/mock_utils.cpp	81.81% <0%> (+10.38%)	:arrow_up:
kvs/src/kvs/gossip_handler.cpp	6.66% <0%> (-0.32%)	:arrow_down:
kvs/tests/route/run_routing_handler_tests.cpp	100% <100%> (ø)	:arrow_up:
kvs/tests/include/lattices/test_map_lattice.hpp	100% <100%> (ø)	:arrow_up:
kvs/include/lattices/core_lattices.hpp	95.65% <100%> (ø)	:arrow_up:
kvs/tests/kvs/server_handler_base.hpp	100% <100%> (ø)	:arrow_up:
kvs/include/utils/server_utils.hpp	64.86% <100%> (-0.93%)	:arrow_down:
... and 47 more

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update abe1173...a0d710d. Read the comment docs.