v0.7

Special thanks to @ploxiln, @mreiferson, @jehiah, @JamesCohen-awin, @omega, @encryptio, @gevorg15, @teepark and all the other contributors!

Here are some changes from the last release:

• tcp listener (#56)
• postfix support (#64, #65)
• configurable udp packet size (#63)
• delete-gauges support (#62)
• sanitized bucket/metric names for graphite (#61, #66)
• support sets (#52)
• support relative operations on gauges (#40)
• negative counter support (#41)
• bug fixes, tooling, test cleanup (#42, #44, #46, #47, #49, #54, #55)