added version property to CombyInterface (fixes #24)

Author: ChrisTimperley

src/comby/binary.py

@@ -31,10 +31,16 @@ class CombyBinary(CombyInterface):
     language: str
         The default language that should be assumed when dealing with source
         text where no specific language is specified.
+    version: str
+        The version of Comby that is used by this binary.
     """
     location = attr.ib(type=str, default='comby')
     language = attr.ib(type=str, default='.c')
 
+    @property
+    def version(self) -> str:
+        return self.call('-version').strip()
+
     def call(self, args: str, text: Optional[str] = None) -> str:
         """Calls the Comby binary.
 

src/comby/interface.py

@@ -15,10 +15,17 @@ class CombyInterface(abc.ABC):
 
     Attributes
     ----------
+    version: str
+        The version of Comby that is provided by this interface.
     language: str
         The default language that should be assumed when dealing with source
         text where no specific language is specified.
     """
+    @property
+    @abc.abstractmethod
+    def version(self) -> str:
+        ...
+
     @property
     @abc.abstractmethod
     def language(self) -> str: