2.0.0 tag

Pubspec 2.0.0-rc2

bcgit#45

Added well named getters for public and private exponents and associated tests.
Added public key exponent field in private key and associated tests.
Updated equality methods, added associated tests.
Updated change log.

v1.0.0

First version supporting Dart 2.0 and Strong Mode

Bump v1.0.0-rc4

bump to 1.0.0-rc3

Release candidate for Dart 2 support