Allow multi-line ENV values

Use regex to parse ENV variable names from .env
For each variable name, find the value of the variable by pulling
the text *between* the current variable and the next variable in
the file (ignoring quotes)

Author: Alexander Mancevice

dotenv/main.py

@@ -14,7 +14,7 @@
 from .compat import StringIO
 
 __escape_decoder = codecs.getdecoder('unicode_escape')
-__posix_variable = re.compile('\$\{[^\}]*\}')
+__posix_variable = re.compile(r'\$\{[^\}]*\}')
 
 
 def decode_escaped(escaped):
@@ -78,12 +78,16 @@ def dict(self):
     def parse(self):
         f = self._get_stream()
 
-        for line in f:
-            key, value = parse_line(line)
-            if not key:
-                continue
+        # Find all variable names in .env
+        fbody = f.read()
+        varexp = r'^(?:export )?([a-zA-Z_][a-zA-Z0-9_]+) *= *[^=\n]'
+        vars = re.findall(varexp, fbody, re.MULTILINE)
 
-            yield key, value
+        # Extract values from text *between* variable names (ignoreing quotes)
+        for key, nxt in zip(vars, vars[1:] + ['$']):
+            valexp = r'{} *= *[\'"]?(.*?)[\'"]? *\n?{}'.format(key, nxt)
+            val = re.search(valexp, fbody, re.MULTILINE | re.DOTALL).group(1)
+            yield key, val
 
         if self._is_file:
             f.close()