Add templating feature

[alFReD-NSH]

This is a nice feature that we can build static parts of a PDF file before, save them, and then later on we put them on the dynamic content for everypage. Though the way I implemented it may not be the best(for example you can switch pages, which you should not, or maybe the fonts may not work), but at the moment it basically works:

I added these functions to public API:

• startTemp() -> starts the templating mode
• endTemp() -> ends the templating mode
• outputTemp() -> which will outputs the template

I added an argument to the end of the constructor function:

• constructor: (@options = {}, temp) in which temp is object that is returned by outputTemp()

Beside that 3 variables:

• haveTemp: false
• isTemp: false
• temp -> which holds the template object

But this is just a work in progress. I'm thinking of adding features such as, building on a pre-built file, or having multiple templates.

[alFReD-NSH]

This is the example:

var pdf = require('./index.js');

var doc = new pdf();
doc.startTemp();
doc.text('im a template!');
doc.endTemp();

var temp = JSON.parse(JSON.stringify( doc.outputTemp() )); // To ensure nothing happens when it is saved

var doc2 = new pdf({}, temp);
doc2.text('hi2');
doc2.addPage();
doc2.text('hi3');
doc2.write('tess.pdf');

[alexandre1985]

Since this feature was introduce long time ago, I would like to now if this feature can now build on a pre-built file, I mean using one file as template?
Thank you