Info on using modifyVars

Brief summary about the function modifyVars.
Fix for usage docs on dumpLineNumbers option
Added link to german translation
Media queries in import statements.
Fixed typos.
Minor change.
Added import variants.
Removed table and changed it to four space indent.
link to ukrainian translation
Add dependency on ruby 1.9.3 as rdiscount doesn't work in 1.9.2
Fix some of the documentation
Details about 1.4.0 beta
Added reference for sqrt, sine and cosine.
Absolute value.
Added tangent.
Added asine.
Added acos and fixed asin.
Added atan.
Changed Pi to pi.
Fixed whitespaces formatting.