Added Revision History and modified .gitignore

Doc/ProblemStatement/.gitignore

 *.aux
 *.log
+*.gz
\ No newline at end of file

Doc/ProblemStatement/Problem_Statement.tex

@@ -20,8 +20,11 @@
 \toprule
 \textbf{Date} & \textbf{Developer(s)} & \textbf{Change}\\
 \midrule
-Date1 & Name(s) & Description of changes\\
-Date2 & Name(s) & Description of changes\\
+Jan 22 & Hongqing & Initial upload\\
+Jan 22 &  Weidong & Spelling Check\\
+Jan 22 & Hongqing & Fixing grammar issus\\
+Jan 22 & Sida & Modification on Section 1.2\\
+Jan 23 & Sida & Modification on Section 1.3\\
 ... & ... & ...\\
 \bottomrule
 \end{tabularx}