Add a unit test for issue-126 

Add a unit test to test to test for aggressive parenthesis removal that causes functional changes.
Fix RHS concat (raised in #330)

When attempting to concat the left-side of the rhs, make sure the rhs is
a string.
Merge pull request #331 from rvanvelzen/rhs-strings-fix

Fix RHS concat (raised in #330)
Merge pull request #330 from markjaquith/master

Unit test to detect issue in 8d14efe for #126 that causes aggressive parenthesis removal, functional differences
Display number of failed tests and corresponding files
Merge branch 'master' of github.com:mishoo/UglifyJS2