[release] prepare for 1.2.6

[release] prepare for 1.2.5

[release] prepare for 1.2.4

[release] prepare for 1.2.3

[maven-release-plugin] copy for tag jruby-rack-1.2.2

[maven-release-plugin] copy for tag jruby-rack-1.2.1

[maven-release-plugin] copy for tag jruby-rack-1.2.0

[build] disable javadoc lint on Java 8

prepare for 1.1.21

prepare for 1.1.20