Add single_line_after_imports fixer

getImportUseIndexes() should not return use statements for traits
feature #860 Add single_line_after_imports fixer (ceeram)

This PR was submitted for the 1.4 branch but it was merged into the 1.5 branch instead (closes #860).

Discussion
----------

Add single_line_after_imports fixer

Replaces #816
Implements #153

Commits
-------

85a5bb9 Add single_line_after_imports fixer