Error: add functions to check more error types. (#945)

There are functions to check if the error is from an array of different
reasons, but there were no functions to check if the failure was due to
the rest of the possible error reasons. This commit adds though.

Fixes #942

src/error.rs

@@ -94,6 +94,30 @@ impl Error {
         false
     }
 
+    /// Returns true if the error is related to the request
+    pub fn is_request(&self) -> bool {
+        match self.inner.kind {
+            Kind::Request => true,
+            _ => false,
+        }
+    }
+
+    /// Returns true if the error is related to the request or response body
+    pub fn is_body(&self) -> bool {
+        match self.inner.kind {
+            Kind::Body => true,
+            _ => false,
+        }
+    }
+
+    /// Returns true if the error is related to decoding the response's body
+    pub fn is_decode(&self) -> bool {
+        match self.inner.kind {
+            Kind::Decode => true,
+            _ => false,
+        }
+    }
+
     /// Returns the status code, if the error was generated from a response.
     pub fn status(&self) -> Option<StatusCode> {
         match self.inner.kind {