Fixed regex statements in parser

This clears up a bunch of `DeprecationWarning`s in pytest

ptulsconv/docparser/ptuls_grammar.py

@@ -67,8 +67,8 @@ protools_text_export_grammar = Grammar(
     fs = "\t"
     rs = "\n"
     block_ending = rs rs
-    string_value   = ~"[^\t\n]*"
-    integer_value  = ~"\d+"
-    float_value    = ~"\d+(\.\d+)?"
-    isp            = ~"[^\d\t\n]*"    
+    string_value   = ~r"[^\t\n]*"
+    integer_value  = ~r"\d+"
+    float_value    = ~r"\d+(\.\d+)?"
+    isp            = ~r"[^\d\t\n]*"    
     """)

ptulsconv/docparser/tagged_string_parser_visitor.py

@@ -18,11 +18,11 @@ tag_grammar = Grammar(
     key_tag        = "[" key "]" word_sep?
     short_tag      = "$" key "=" word word_sep?
     full_text_tag  = "{" key "=" value "}" word_sep?
-    key            = ~"[A-Za-z][A-Za-z0-9_]*"
-    value          = ~"[^}]+"
+    key            = ~r"[A-Za-z][A-Za-z0-9_]*"
+    value          = ~r"[^}]+"
     tag_junk       = word word_sep?
-    word           = ~"[^ \[\{\$][^ ]*"
-    word_sep       = ~" +"
+    word           = ~r"[^ \[\{\$][^ ]*"
+    word_sep       = ~r" +"
     modifier       = ("@" / "&") word_sep?
     """
 )