Merge pull request #1 from oneplus1000/master

refactoring code
Merge pull request #2 from oneplus1000/master

Add underline
Merge branch 'master' of github.com:signintech/gopdf
Reduction pdf(output) file when the image is repeated.
clean code
clean code
fix done : Reduction size of pdf(output) file, when the image is repeated. :-)