docs: Revert documents

v0.2.3 still requires `extern crate sailfish_macros;`

Author: Kogia-sima

README.md

@@ -31,6 +31,7 @@ Dependencies:
 ```toml
 [dependencies]
 sailfish = "0.2.3"
+sailfish-macros = "0.2.3"
 ```
 
 Template file (templates/hello.stpl):
@@ -48,6 +49,9 @@ Template file (templates/hello.stpl):
 Code:
 
 ```rust
+#[macro_use]
+extern crate sailfish_macros;  // enable derive macro
+
 use sailfish::TemplateOnce;
 
 #[derive(TemplateOnce)]

docs/en/docs/getting-started.md

@@ -29,6 +29,9 @@ templates/
 Import the sailfish crates:
 
 ```rust
+#[macro_use]
+extern crate sailfish_macros;  // enable derive macros
+
 use sailfish::TemplateOnce;  // import `TemplateOnce` trait
 ```
 

docs/en/docs/installation.md

@@ -5,4 +5,12 @@ In order to use sailfish templates, you have add two dependencies in your `Cargo
 ```toml
 [dependencies]
 sailfish = "0.2.3"
+sailfish-macros = "0.2.3"
 ```
+
+`sailfish` crate contains runtime for rendering contents, and `sailfish-macros` serves you derive macros to compile and import the template files.
+
+These crates are separated so that Rust compiler can compile them independently. This separation makes your compilation faster!
+
+!!! Warning
+    Make sure that the `sailfish-macros` version is larger than `sailfish`, otherwise the compilation may fail.