this mainly allows us to check if an account has a certain role and thus
if the account can call specific contract functions.
At some point we might want to extend that to support the check if an
account can call the function. For that we would need to have a mapping
between function names and roles, which we have not right now.
AppIds are used to lookup the actual contract addresses of each app.
Because of different registry names (open.aragonpm.eth vs. aragonpm.eth)
we have to use different ids in the local dev chain and in the
testnet/mainnet. To allow this we need to set the appids dynamically.
There is an open aragon issue to solve this and also allow to use
open.aragonpm.eth in the devchain by default.
https://github.com/aragon/aragen/issues/10
This allows to filter contributors by the account entries.
For example:
```js
Contributor.filterByAccount({site: 'github.com'}); // returns all
contributors with github account
Contributor.filterByAccount({site: 'github.com', username: 'bumi'});
// returns bumi
```
This moves the Kredits initialization to the instance which allows us to
be more flexible with handling contract addresses.
Example:
var k = new Kredits(provider, signer, {Registry: '0xabc'});
k.init().then((kredits) { ...});
var k = new Kredits(provider, signer, {Contributors: '0xabc'})
k.Contributor.add(...);
This allows to provide options like gas price/limit settings for the
state changing contract calls.
These options are simply passed to the ethers contract instance.
We need to provide the gas limit when using the jsonrpc provider.
(ganache failed with revert if not enought gas was provider)
