Added helper function to generate tags. Need Andres to look into this
	modified:   ext/tag.c
	modified:   ext/tag.h
Created tagHtml function. Sending it upstream for Andres to have a look at
	modified:   tag.c
	modified:   tag.h

Conflicts:
	ext/tag.c
TagHtml: Added test and corrected wrong pointer. Upstream for Andres to check
	modified:   ext/tag.c
	modified:   php-tests/tests/Phalcon/Tag/UnitTest.php
Added phalcon_eol function to add PHP_EOL to elements;
	modified:   ext/tag.c
Replaced EOL references in Tag with phalcon_eol()
	modified:   ext/tag.c
Added phalcon_eol function to return PHP_EOL when requested
	modified:   ext/kernel/string.c
	modified:   ext/kernel/string.h
Corrected definition of phalcon_substr
	modified:   ext/kernel/string.h
Removed the phalcon_eol from the tag component - moved to kernel/string
	modified:   ext/tag.c