Add simple optimization for empty-string concats.

ref. #43
don't change order in binary expressions if both operands have side effects
Merge branch 'optimize_concat' of https://github.com/rvanvelzen/UglifyJS2 into rvanvelzen-optimize_concat
optimize constant switch blocks

ref. mishoo/UglifyJS#441
better solution for the last test in constant switch folding
Add support for somewhat preserving line numbers.

Usage: uglifyjs2 -b "beautify=0,preserve_line=1" /path/to/js

ref #46
retain (1,eval) as is when it's the expression of an AST_Call

otherwise we change the meaning of eval from global to lexical.
fix #51
rename the npm package to "uglify-js" and cli tool to "uglifyjs"
fix for https://github.com/mishoo/UglifyJS/issues/474
v2.2.1
fix #55
Fixed reading from STDIN.
Merge pull request #58 from roxeteer/master

Fixed reading from STDIN
Don't messup compressor stack while optimizing Switch

Fix #59
Add test for issue #59
Revert "Fixed reading from STDIN."

It breaks usage like this:

    echo '...code...' | uglifyjs

This reverts commit e48802ad291fae5a16f2d23cbd25a0c433cdbe48.
When hoisting variables, try to merge in assignments that follow.
small improvement on merging assignments into hoisted vars
Add proper parens in "NoIn" expressions.

fix #60.