Documentation update for setup and a small compile fix (#81)

thanks!

This fix is very important, so I will merge it.

I'm sorry, there is not enough documents...

README.md

@@ -185,6 +185,8 @@ IROHA_HOME := iroha's root
 ## Requirement
 ```
 cmake(3.5.2)
+gRPC
+LevelDB
 ```
   
 ## Recommended
@@ -194,9 +196,10 @@ fabric3 (python library, not hyperledger/fabric)
 
 ## Installation
 ```
-$ git submodules init
-$ git submodules update
+$ git submodule init
+$ git submodule update
 $ mkdir build
+$ cd build
 $ cmake ..
 $ make
 ```
@@ -206,6 +209,16 @@ or
 $ fab deploy
 ```
 (in local)  
+
+### Rebuilding gRPC stubs
+
+This step should only be necessary if protobuf definitions changes, or version of gRPC or protoc has been updated.
+
+(invoked from $IROHA_HOME)
+```
+protoc  --cpp_out=core/infra/connection core/infra/connection/connection.proto
+protoc  --grpc_out=core/infra/connection  --plugin=protoc-gen-grpc=`which grpc_cpp_plugin` core/infra/connection/connection.proto
+```
   
 ## Authors
 

core/validation/transaction_validator.hpp

@@ -30,8 +30,6 @@ limitations under the License.
 
 namespace transaction_validator {
 
-    using transaction::Transaction;
-
     template<typename T>
     bool isValid(const std::unique_ptr<T>& tx);