Float support

New

• Added support for floats (#8, 🎩 @tgriesser).
• Added support for ISO-8859-1 IVAR encoding (#8, 🎩 @tgriesser).
• Removed support for node 0.10 and 0.12.

Improved

• Upgraded dependencies.
• Replaced Code Climate with Codecov.
• Added test coverage.