“Happy Birthday Justin Bieber” – said everyone the pop star knows, except Selena Gomez, who didn’t attend the bash. On Sunday March 1st Justin Bieber turned 21 years ol d (which really is ironic since he has been partying at clubs for how many years now). Justin Bieber’s birthday is practically a national holiday on the internet, but one person is NOT sending Biebs any warm wishes, his ex-girlfriend of three years Selena Gomez, who is now dating DJ Zedd.Zedd is madly in love with Selena Gomez, so you can imagine how he felt when she dished to V Magazine in a recent interview that she “would always love” her ex Justin Bieber , and pals of Justin’s revealed that Selena has been blowing up his phone – but he won’t take her calls. Zedd will not let Selena Gomez out of his sight, that became apparent at the Vanity Fair Oscar Party where insiders blabbed that the DJ was smothering fellow “I Want You To Know” singer.When Justin’s 21st birthday neared his camp began making plans for the elabora…