Change the version to 2.0.0.BUILD-SNAPSHOT to support Spring Boot 2.0

[qiyi]

Change the version to 2.0.0.BUILD-SNAPSHOT to support Spring Boot 2.00.RELEASE and Spring Cloud 2.0.0.x, #46

1. Change the version to 2.0.0.BUILD-SNAPSHOT
2. Merge the Removes EtcdLifecycle in favor of AutoRegistration and ServiceRegistry APIs #43 from @venilnoronha for the EtcdLifecycle can't work now
3. Upgrade the etcd version to v3.3.1 for ci

[qiyi]

it seems that generating readme failed.

Error opening script file: /home/travis/build/spring-cloud-incubator/spring-cloud-etcd/docs/target/build-docs/ruby/generate_readme.sh (No such file or directory)
Permissions.java:196:in `checkExit': org.apache.tools.ant.ExitException: Permission ("java.lang.RuntimePermission" "exitVM") was not granted.
	from Runtime.java:107:in `exit'
	from System.java:971:in `exit'
	from Main.java:199:in `main'
	from NativeMethodAccessorImpl.java:-2:in `invoke0'
	from NativeMethodAccessorImpl.java:62:in `invoke'

[qiyi]

ping @spencergibb , Can you help to review this PR?

[spencergibb]

After Finchley is released.

[qiyi]

@spencergibb Upgraded to Finchley now -.-

[qiyi]

@spencergibb help to review this PR please.

[qiyi]

Hi, @spencergibb , do you have time to review this PR

[spencergibb]

I'm on holiday for the next week, hopefully after.