Implement postProcessor callback feature for less.ls browser environment #1835

Add `jasmine:postProcessor` task and corresponding spec as well
Update README.md
update readme
Change wiki link to website link
Fixed a typo for 1.7.0: `@supports` -> `@keyframes`
README.md: LESS -> Less
Let `luma` follow spec

The `luma` function found in LESS is not implemented as defined in the specification (http://www.w3.org/TR/2008/REC-WCAG20-20081211/#relativeluminancedef).
Let tests reflect output of new luma function.
Add test case were luminance is not equal to luma.
Fixed that in some situations a mixin call into a referenced file wouldn't import media queries. Fixes #1469
Fix a small scope issue with mixins when using parent selectors, introduced in 1.6.2. Fixes #1877
when in lint mode, report errors from creating css. Fixes #1786
Do not evaluate css with guards if the guards fail. Fixes #1873
Merge branch 'master' of https://github.com/cloudhead/less.js
tweak the log levels. Fixes #1856
Merge branch 'master' of https://github.com/cloudchen/less.js

Conflicts:
	lib/less/browser.js
add browser details to changelog
add-in more changes to the changelog
call callback if exception whilst calling toCSS. Fixes #1816
re-implement pull request #1701 - still allow log level to be configurable in dev mode