Simplify package exceptions set.
Allow positional arguments in test invocation.
Test read_cask_file properly.
Detect markup function by file name.
Add each_template iterator and render function.

Render function will write rendered template to file system.
Correct used exceptions in package module.
Render each available template in main function.
Allow to run mkreadme as a module.
Move console entry point to core module.
Specify console entry points.
Fix each_template iterator for python2.