Merge https://github.com/less/less.js into rhino

Conflicts:
	README.md
Properties merging should work also inside directives #2035

Fixes issue #2035 - property merge inside @font-face. The _mergeRules function is now called also for directives with rules. It used to be called only for rulesets.

I had to turn off jasmine tests for merge.less, because it was replacing all urls by their assumed full paths. For example, the url(something.eot) was changed into url(http://localhost:8081/test/less/something.eot). The result did not matched with expected css and failed.

Note: I'm not sure why values order in source map changed. It does not seem to be caused by my change, it was failing before I made them.
Putting readme.md into its original state. Also, travis failed with weird
message and I want to see what it will do this time.

Previous travis error:
>> PhantomJS has crashed. Please read the crash reporting guide at
>> https://github.com/ariya/phantomjs/wiki/Crash-Reporting and file a bug
>> report at https://github.com/ariya/phantomjs/issues/new with the crash
>> dump file attached: /tmp/7685d81d-94f5-1db7-12c9006e-72f80442.dmp 0 [
>> 'PhantomJS has crashed. Please read the crash reporting guide at
>> https://github.com/ariya/phantomjs/wiki/Crash-Reporting and file a bug
>> report at https://github.com/ariya/phantomjs/issues/new with the crash
>> dump file attached: /tmp/7685d81d-94f5-1db7-12c9006e-72f80442.dmp' ]
Merge https://github.com/less/less.js into font-face-property-merge-2-2035

Conflicts:
	test/sourcemaps/basic.json
Moved @font-face property merge test into urls.less and re-enabled
merge.less in jasmine tests.
Merge pull request #2121 from SomMeri/font-face-property-merge-2-2035

Properties merging should work also inside directives #2035