Make the DirectiveProcessor encoding aware

In Ruby 1.9, the directive_processor.rb source file defaults to US-ASCII
as it doesn't contain a magic comment, meaning the String initialised in
@result gets a US-ASCII encoding.

This means that when content is concatenated onto @result (e.g. in
process_source), Ruby will maintain the US-ASCII encoding, provided the
content being concatenated contains no non-ascii chars.

The changes in this commit force the encoding of the resulting string to
be that of the body, because conceptually that is the string we are
"concatenating" with.
Build on Ruby 2.0
sass now prefers partials over fullnames

nex3/sass@6cc01962be2203b829616de4b33514ad5c7188d2
Fix brittle size assertion
Expect generic execjs error
Update assertion for CoffeeScript output change
Gotta be a runtime error
Merge branch 'make-directive-processor-encoding-aware' of git://github.com/lmars/sprockets into lmars-make-directive-processor-encoding-aware
Merge branch 'lmars-make-directive-processor-encoding-aware' into fix-build
Fix bundled source original encoding
Should actually be read as UTF8
Merge pull request #429 from sstephenson/fix-build

Fix Travis Build