Create button plugin

Add ButtonPlugin class
Add ButtonPluginTest class
Merge branch 'master' into create-button-plugin
Create button plugin

Add ButtonPlugin class
Add ButtonPluginTest class
Modify get url
Change no parameter

if no parameter then href is "#"
Change format for navi

Delete format for navi
Resolve Conflict
Merge branch 'master' into create-button-plugin
Fix test and spaces
Merge pull request #35 from toiee/create-button-plugin

Create button plugin