Avoid _monitor() fn hop inside ce.fire()

By checking `is monitored` criteria outside function.

May revisit to remove check inside _monitor later, bif we can do so for all _monitor
calls, but it's a fairly rare use case, so not that critical a path, so not worried about it

Testing
-------

All tests pass, except for known yogi test/io test failure (fails prior to this change also and in clean dev-3.x)

[Total]: Passed: 10725 Failed: 1 Total: 10811 (ignored 85) (8 minutes, 26 seconds)

[io-base Test Suite]: Passed: 39 Failed: 1 Total: 40 (ignored 0) (1.372 seconds)
    testPOSTWithNoData

Numbers
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Chrome 25

This commit:

new BaseCore() x 58,892
new Base() x 24,668
Subscribe + Fire - 10 different events x 8,315
Fire - 10 different events, no listeners x 316,605
Publish - 10 different events x 44,614
EventTarget Construction + Publish(foo) + Subscribe(foo) + Fire(foo) - 10 listeners x 24,552
EventTarget Construction + Publish(foo) + Subscribe(foo) + Fire(foo) - 2 listeners x 67,265
EventTarget Construction + Publish(foo) + Fire(foo) - no listeners x 270,168
Fire With Payload - 10 listeners x 253,889
Fire - 10 listeners x 320,085
Fire With Payload - 2 listeners x 434,377
Fire - 2 listeners x 625,443
Publish x 470,998

Prior commit:

new BaseCore() x 55,420 ops/sec ±0.69% (92 runs sampled)
new Base() x 23,924 ops/sec ±1.53% (93 runs sampled)
Subscribe + Fire - 10 different events x 7,778 ops/sec ±1.71% (93 runs sampled)
Fire - 10 different events, no listeners x 199,091 ops/sec ±0.81% (90 runs sampled)
Publish - 10 different events x 45,317 ops/sec ±0.55% (95 runs sampled)
EventTarget Construction + Publish(foo) + Subscribe(foo) + Fire(foo) - 10 listeners x 22,818 ops/sec ±1.55% (95 runs sampled)
EventTarget Construction + Publish(foo) + Subscribe(foo) + Fire(foo) - 2 listeners x 62,990 ops/sec ±1.49% (94 runs sampled)
EventTarget Construction + Publish(foo) + Fire(foo) - no listeners x 245,377 ops/sec ±2.05% (93 runs sampled)
Fire With Payload - 10 listeners x 234,145 ops/sec ±1.28% (89 runs sampled)
Fire - 10 listeners x 315,210 ops/sec ±0.58% (97 runs sampled)
Fire With Payload - 2 listeners x 320,415 ops/sec ±0.79% (96 runs sampled)
Fire - 2 listeners x 462,005 ops/sec ±0.38% (94 runs sampled)
Publish x 409,211 ops/sec ±0.37% (93 runs sampled)