Preserve casing of keywords (#31)

* Preserve casing of keywords

* Add test. Fix vari relation bug

Author: natefaubion

src/SqlSquared/Parser.purs

@@ -578,8 +578,7 @@ tableRelation = do
 
 variRelation ∷ ∀ m t. SqlParser m t (Sig.Relation t)
 variRelation = do
-  operator ":"
-  vari ← ident
+  vari ← variableString
   a ← PC.optionMaybe do
     _ ← keyword "as"
     ident

src/SqlSquared/Parser/Tokenizer.purs

@@ -226,7 +226,7 @@ notQuotedIdentOrKeyword = do
     str = S.fromCharArray $ A.cons first other
     low = S.toLower str
   pure if Set.member low keywords
-    then Kw low
+    then Kw str
     else Identifier str
 
 stringLit ∷ ∀ m. Monad m ⇒ P.ParserT String m Token

test/src/Parse.purs

@@ -184,6 +184,10 @@ testSuite1 = do
     select foo as `between` from bar
   """
 
+  parseSucc """
+    select foo from :From
+  """
+
 testSuite2 ∷ ∀ e. TestSuite (testOutput ∷ Console.TESTOUTPUT | e)
 testSuite2 = do
   parseSucc """