Add adaptive precision for values

[enescakir]

Number of the digits after the decimal point isn't enough especially for cryptocurrencies.

In this PR, we decide it for each stock adaptively. Yahoo Finance shows max 4 digits min 2 digits after dot.

       stock < 10       --->   precision: 4     i.e.: 0.4375, 1.5436
 10 <= stock < 100      --->   precision: 3     i.e.: 10.543
100 <= stock            --->   precision: 2     i.e.: 100.30, 49435.97

Fixes #86

[achannarasappa]

Looks good to me thanks for the PR!