Issue #99 Applying validators fees (#107)

* domain - big_num - impl AddAssign

* domain - DomainError - add a `RuleViolation`

* domain - BalancesMap:
- Wrap the BTreeMap in our own type
- Impl the applying of validation fees

* domain - Cargo.toml - add `fake` and `rand` for testing as they are options otherwise

* [test] domain - balances_map - apply zero fees

* domain - DomainError - add `derive(PartialEq)`

* [test] domain - balances_map - test when fees > deposit + clean test code

* domain - big_num - impl `Mul<Ratio<BigUint>>` until we impl Integer for BigNum

* [test] domain - balances_map - applying fee correctly with partial distribution

* domain - Cargo.toml - add `num-traits` & `num-derive`

* domain - big_num - use derives and clean code with Ratio

* domain - big_num - remove `ratio()` method

* domain - big_num - fix bug with `0` after multiplication with `Ratio`

* [test] domain - balances_map - applying fees correectly

Author: elpiel

Cargo.lock

@@ -16,11 +16,17 @@ serde = { version = "^1.0", features = ['derive'] }
 serde_json = "1.0"
 serde-hex = "0.1.0"
 # Domain
-num-bigint = { version = "0.2", features = ["serde"] }
 chrono = { version = "0.4", features = ["serde"] }
 time = "0.1.42"
 hex = "0.3.2"
+# Numbers - BigNum, Numbers, Traits and Derives
+num-bigint = { version = "0.2", features = ["serde"] }
 num = "0.2.0"
+num-traits = "0.2"
+num-derive = "0.2"
 # Fixtures
 fake = { version = "^1.3", features = ["chrono"], optional = true }
 rand = { version = "^0.6", optional = true }
+[dev-dependencies]
+fake = { version = "^1.3", features = ["chrono"] }
+rand = { version = "^0.6" }