update doc with exception management

Author: codlab

README.md

@@ -4,10 +4,18 @@
 
 ## Import
 
+In your build.gradle file, add the following :
+
 ```
-TODO
+repositories {
+    maven {
+        url  "https://dl.bintray.com/codlab/oss" 
+    }
+}
 ```
 
+
+
 ## Usage
 
 The minimalistic Promise can be write such as :
@@ -24,34 +32,34 @@ The minimalistic Promise can be write such as :
 You can chain the promise with the following sample:
 
 ```java
-        Promise<Boolean> promise = new Promise<>(new PromiseSolver<Boolean>() {
-            @Override
-            public void onCall(@NonNull Solver<Boolean> solver) {
-                solver.resolve(false);
-            }
-        });
-
-        //chain it
-        promise
-                .then(new PromiseExec<Boolean, String>() {
-                    @Override
-                    public void onCall(@Nullable Boolean result, Solver<String> solver) {
-                        solver.resolve("previous result is := " + result);
-                    }
-                })
-                .then(new PromiseExec<String, Integer>() {
-                    @Override
-                    public void onCall(@Nullable String result, Solver<Integer> solver) {
-                        solver.resolve(result.length());
-                    }
-                })
-                .then(new PromiseExec<Integer, Object>() {
-                    @Override
-                    public void onCall(@Nullable Integer result, Solver<Object> solver) {
-                        //TODO something with the result which is the length of the appended false
-                    }
-                })
-                .execute();
+    Promise<Boolean> promise = new Promise<>(new PromiseSolver<Boolean>() {
+        @Override
+        public void onCall(@NonNull Solver<Boolean> solver) {
+            solver.resolve(false);
+        }
+    });
+
+    //chain it
+    promise
+            .then(new PromiseExec<Boolean, String>() {
+                @Override
+                public void onCall(@Nullable Boolean result, Solver<String> solver) {
+                    solver.resolve("previous result is := " + result);
+                }
+            })
+            .then(new PromiseExec<String, Integer>() {
+                @Override
+                public void onCall(@Nullable String result, Solver<Integer> solver) {
+                    solver.resolve(result.length());
+                }
+            })
+            .then(new PromiseExec<Integer, Object>() {
+                @Override
+                public void onCall(@Nullable Integer result, Solver<Object> solver) {
+                    //TODO something with the result which is the length of the appended false
+                }
+            })
+            .execute();
 ```
 
 You can do whatever you want in the promise or the chained execution (Thread, Async post, Bugs, Save a cat)
@@ -71,7 +79,37 @@ Once one of those 2 calls are made, the promise will start resolving itself.
 Note that it is the best practice to manage the execution flow using `error(<ErrorPromise>)` to be sure
 to grab any issues the Promise resolution could throw !
 
+Example : 
+```
+    new Promise<String>(new PromiseSolver<String>() {
+            @Override
+            public void onCall(@NonNull Solver<String> solver) {
+                solver.resolve(null);
+            }
+        })
+        .then(new PromiseExec<String, String>() {
+            @Override
+            public void onCall(@Nullable String result, @NonNull Solver<String> solver) {
+                //exception thrown right here
+                solver.resolve(result.toLowerCase());
+            }
+        })
+        .then(new PromiseExec<String, Void>() {
+            @Override
+            public void onCall(@Nullable String result, @NonNull Solver<Void> solver) {
+                System.out.println("you should not see this");
+            }
+        })
+        .error(new ErrorPromise() {
+            @Override
+            public void onError(@NonNull Throwable error) {
+                System.out.println("error catched");
+                error.printStackTrace();
+            }
+        });
+```
 
+Note : error() calls execute
 ## Contributing
 
 When contributing to this repository, please first discuss the change you wish to make via issue,