Merge pull request #82 from slafs/master

added integration test for new shlex env parsing
load export implementation from entry points.
load template according to package name.
add new section into docs to introduce exporting plugin.
describe the get_template method of BaseExport.
break lines too long.
rename the name of entry point.
Merge pull request #83 from tonyseek/export-plugin-mechanism

Load exporting formats as entry points.