Base64 encode source maps

This prevents some edge cases where encodeURIComponent fails to create a valid
source map.

This particular edge case was identified when trying to create source maps for
the lesshat mixin library.

Signed-off-by: Tim Smart <tim.smart@designworks.co.nz>
Merge pull request #2045 from tim-smart/feature/sourcemaps-base64

Base64 encode source maps
suport passing strings to paths
Merge branch 'master' of https://github.com/less/less.js
fix regression with jsifying code - all dimensions would be rounded. Fixes #2057
1.7.2 release
don't round values returned by colour query functions.
missing distribution files
Merge pull request #2062 from seven-phases-max/not-rounded-color-queries

Don't round values returned by colour query functions.
Fix backtracking on multiplication to support dimension /|* keyword, with or without strict maths. Fixes #2066.
Merge branch 'master' of https://github.com/less/less.js
merge from master