accumulator 0.7.0

A key-value store limited by size or time, allowing accumulation of multiple values under a single key.
Documentation
# Accumulator - Change Log

## [0.7.0]
- Use rust 1.22.1 stable / 2017-11-23 nightly
- rustfmt 0.9.0 and clippy-0.0.174

## [0.6.0]
- Use rust 1.19 stable / 2017-07-20 nightly
- rustfmt 0.9.0 and clippy-0.0.144
- Replace -Zno-trans with cargo check
- Update CI scripts and README

## [0.5.0]
- Add/rename `quorum` and `set_quorum` methods.
- Some documentation updates.

## [0.4.0]
- Use `HashSet` instead of `Vec`, so that adding the same entry multiple times
  is only counted as 1.

## [0.3.0]
- Move from the time crate to std::time.

## [0.2.0]
- Fixed Clippy warnings
- Updated dependencies

## [0.1.4]
- Removed a deprecated lint check
- Minor cleanup and added clippy

## [0.1.3]
- Remove wildcards from dependencies

## [0.1.2]
- Updated in line with lru_time_cache 0.2.2

## [0.0.4]
- Added a setter function for threshold size

## [0.0.3]
- Updated dependency's version

## [0.0.1 - 0.0.2]
- Initial implementation