Removed unused functions and rewrote others using modern browser capabilities

[fabiomcosta]

mixpanel-js is big.

The approach I'm taking here is to use modern browsers capabilities to decrease the code size, but a bigger win might come from splitting the lib up into other smaller libs that each can attend a specific use case/feature.
Ex: one for notifications, another for user tracking, etc.

This discussion started at #128

• _.identity -> removed, unused
• _.timestamp -> removed, unused
• _.JSONEncode -> JSON.stringify
• _.JSONDecode -> JSON.parse
• _.trim -> replaced with String.prototype.trim
  http://kangax.github.io/compat-table/es5/#test-String_properties_and_methods_String.prototype.trim_a_href=_https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/Trim_title=_MDN_documentation_img_src=_../mdn.png_alt=_MDN_(Mozilla_Development_Network)_logo_width=_15_height=_13_/_/a_nbsp;
• _.bind -> replaced with Function.prototype.bind
  http://kangax.github.io/compat-table/es5/#test-Function.prototype.bind


  
*_.utf8Encode -> became much smaller, based on http://ecmanaut.blogspot.ca/2006/07/encoding-decoding-utf8-in-javascript.html


• _.base64Encode -> became much smaller using btoa, and it was the only function using utf8Encode, so I inlined it there.

  
http://caniuse.com/#feat=atob-btoa
  NOTE: btoa is not support on IE9 and before, is this a problem?
• _.dom_query -> replaced by a much smaller version using querySelectorAll

  http://caniuse.com/#feat=queryselector
  NOTE: querySelectorAll is well supported only by IE9+, is this a problem?

Numbers:
mixpanel.min.js: 59.4K -> 52K (-7.4K, 13.5% reduction) (non-gzipped)

Please let me know if there is more unused code or if there is anything else I can improve further.

[fabiomcosta]

@jbwyme any change this will could be merged? I just wanted to start a conversation.
What are the browsers this library has to support?

[ghost]

@tdumitrescu @jbwyme any update on this?

[hackuun]

+1 any news?

[fabiomcosta]

Let me know if you're moving forward with this, I can solve conflicts to get it merged, but since I didn't get an answer from the beginning I'm not going to do these changes now before I get a clear confirmation.

[fabiomcosta]

Let me know if you're moving forward with this, I can solve conflicts to get it merged, but since I didn't get an answer from the beginning I'm not going to do these changes now before I get a clear confirmation.