change version to 0.5.0-SNAPSHOT
Comments format and improvement
add .travis.yml for travis building
delete test output
refactor code
improve some API comments
add more comments
1. kmeans example 2. yarn nn example 3. guagua shell refactor to hadoop like
Add attachment field for master and worker context. This attachment can be set by user for transfering objects between MasterComputable and MasterInterceptors
change  kmeans to support random choose k initial centriods
changed for 0.4.1 release
Merge branch 'release-0.4.1-b'

Conflicts:
	README.md