!calc drops precision of floating point numbers

**Now**:
```
<aodhneine>: !calc 0.30000000000000004 + 0.1
<MrBotka>: 0.4
```

**Expected**:
```
<aodhneine>: !calc 0.30000000000000004 + 0.1
<MrBotka>: 0.40000000000000004
```