handle sort more precisly and MinKey/MaxKey
Merge branch 'issue78' into minkey_maxkey

Conflicts:
	src/main/java/com/foursquare/fongo/impl/ExpressionParser.java
	src/test/java/com/foursquare/fongo/FongoTest.java
Merge branch 'master' into minkey_maxkey
for a more accurate comparison
throw Exception when unknown
Merge branch 'issue78' into minkey_maxkey
simplify sorting
Merge branch 'master' into minkey_maxkey

Conflicts:
	src/main/java/com/foursquare/fongo/impl/ExpressionParser.java
Merge remote-tracking branch 'github/master' into minkey_maxkey

Conflicts:
	src/main/java/com/foursquare/fongo/impl/ExpressionParser.java
compareObjects return Integer only on private scope
Merge pull request #81 from twillouer/minkey_maxkey

Minkey maxkey