Market bug fixes

[svk31]

Also includes an update to the README for Ubuntu 16.x

[roadscape]

Awesome, just 2 notes:

1. With regards to the MySQL note, is it necessary to use root or could we include instructions for creating something like a steem user if it's just as straightforward? (I'm assuming root does not work like it used to for enhanced default security out of the box?)
2. buy_price_warning and sell_price_warning were originally used to warn the user if the "effective" rate differed from the "entered" rate by more than 1%. This can happen when the amounts involved are small -- for example:
   
   (The entered rate is 0.010 SD/STEEM, but the effective rate is 0.00666.... The "Price" field becomes grayed as a cheap way to alert the user.)
   Overall, since this 'quirk' only applies to small amounts, it's of relatively low importance. And although it did cause enough confusion to be reported, the case you repurposed these props for will be useful for more users and greater amounts.
   If there is a simple way to warn the user in these cases too it would be nice to have; otherwise, let's leave it as-is.

[valzav]

@roadscape could you please review?

[svk31]

For the mysql, that's beyond me tbh, I just found those instructions on stackoverflow as other users have reported similar issues. I think that the mysql root user should be independent from your OS root user, but for some reason that's not the case in Ubuntu 16.x.

About the percentDiff method, it must've gotten bugged at one point because it was always returning 0 since the two amounts input were always the same.

The greying out still happens, but now whenever the price differs by 15% or more from the market prices. The 15% is completely open to tuning, it's just a number that seemed ok to me.

[roadscape]

About the percentDiff method, it must've gotten bugged at one point because it was always returning 0 since the two amounts input were always the same.

It would probably return 0 for most values which are not in the sub-10 satoshi ranges. It does seem better to repurpose it for this case; 15% seems reasonable. I'll give it a final test and merge today.

[jcalfee]

Great, thanks for the mysql fix. That is tricky.

In the future we should probably use a bound component <input value={this.state.buySteem_price} instead of setting the value directly. I'll just assume that was a more invasive change.
componentWillReceiveProps() { ... if (this.refs.buySteem_price) this.refs.buySteem_price.value = parseFloat(lowest_ask).toFixed(6); ... }

.. or correct me if I'm missing something. Thanks..

[svk31]

Yes the value change via refs was just to stay in line with how it was already being done.