Fix reference to Context in redis_command macro (#109)

Errant identifier did not properly reference crate context, which made
the results dependent on the namespace of the usage environment.

Author: slavak

src/macros.rs

@@ -16,16 +16,17 @@ macro_rules! redis_command {
             argv: *mut *mut $crate::raw::RedisModuleString,
             argc: c_int,
         ) -> c_int {
-            let context = Context::new(ctx);
+            let context = $crate::Context::new(ctx);
 
             let args_decoded: Result<Vec<_>, $crate::RedisError> =
                 unsafe { slice::from_raw_parts(argv, argc as usize) }
                     .into_iter()
                     .map(|&arg| {
                         $crate::RedisString::from_ptr(arg)
                             .map(|v| v.to_owned())
-                            .map_err(|_|$crate::RedisError::Str(
-                                "UTF8 encoding error in handler args"))
+                            .map_err(|_| {
+                                $crate::RedisError::Str("UTF8 encoding error in handler args")
+                            })
                     })
                     .collect();