Library can't parse multiline values properly

[x1unix]

Library doesn't parse multi-line variable values properly.

Input:

URLS="foo
bar"

Expected:

map[string]string{
  "URLS": "foo\nbar",
}

Got:

map[string]string{
  "URLS": "foo",
  "bar",
}

[x1unix]

@joho I'm already working on fix, but this requires a major rewrite of parser implementation

[x1unix]

@joho added PR with issue fix - #118.

Please take a look

[joho]

Duplicate of #64