Changes to allow filtering by regex

Hi!

I've forked the project in order to make some chanhges that I find usefull.

They are just some litle changes. The idea behind them is the following:
Sometimes, in the company I work, whe deploy a new version of any application, and we see logs in order to know if these new version is working fine. In such situations, sometimes, we just want to see only if an Error log is generated. So, to allow seeing only errors logs (or any log matching with any desired regular expression) in a Stream or in a History screen, I've made some changes.

The changes where made only in the client, without modifying any previous behavoiur of log.io.
Specifically, the changes are:

index.html
	 Line 86: <div class="screen-filter"><a href="#" class="result-count"></a><input type="text" class="inactive" name="filter" title="Regex Filter" value="Regex Filter"/></div>
	 Line 97: <div class="screen-filter"><a href="#" class="result-count"></a><input type="text" class="inactive" name="search" title="Regex Filter" value="Regex Filter"/></div>
	 
web_client.css:
	From Line 144 to Line 186: Added styles for screen_filter
	
stream.js:
	It was added the filter property when a new Stream is created (this.filter = null)
	Lines 56 to 65: add the condition which allows filtering by regex
		
history.js: Same as stream.js

renderers.jquery.js 
	Lines 125 to 133: was added a condition to allow filtering logs by regex in stream
	Lines 227 to 232: Was added a condition to allow filtering logs by regex in history (similar to the previous lines).

I wish you accept my pull request!!!

Best Regards!!