chore(Makefile): Add Makefile to build MissingBlobs.jar

Create a MANIFEST.MF as well.

Author: joshchoo

META-INF/MANIFEST.MF

@@ -0,0 +1 @@
+Main-Class: Main

Makefile

@@ -0,0 +1,4 @@
+default:
+	javac -d . src/*.java
+	jar cvmf META-INF/MANIFEST.MF MissingBlobs.jar *.class
+	rm *.class

README.md

@@ -45,10 +45,9 @@ check whether any of these dependencies are not present.
 - java compiler
 
 ### Building
-In the source file directory, execute:
+In the root directory of the repo, execute:
 ```
-$ javac *.java
-$ jar -cvfe MissingBlobs.jar MissingBlobs *.class
+$ make
 ```
 
 A runnable `MissingBlobs.jar` will be produced.