Bump to v0.8.0

Bump to v0.7.1

Bump to v0.7.0

Update changelog

Bump to v0.6.1

Merge pull request stellar-deprecated#296 from nullstyle/out-of-date

Allow horizon operators to define a "Staleness Threshold" that, when passed, disables historical data requests

Bump to v0.5.1

Bump to 0.5.0

Bump to v0.4.0

Update README, bump to v0.3.0