Update dispute properties

[satello]

Goes with kleros/kleros-store#34

• Removes unused data points and restructures shape of disputeData so that data on individual appeals can be returned.
• DRY out open dispute fetching

Example of disputeData:

{ 
      arbitrableContractAddress: '0xdd30bf263e5fe1da07ddb5326fefdf17972663ce',
      arbitrableContractStatus: 4,
      arbitratorAddress: '0x405b80b0342c76fcb4ee295b74e232023019756c',
      partyA: '0xccc6366dc9da1362da4844372ac2ad849cd7f3f2',
      partyB: '0xcb045d43381cceebd94a1245ff4bc81108033488',
      disputeId: 0,
      firstSession: 1,
      lastSession: 1,
      numberOfAppeals: 0,
      disputeState: 3,
      disputeStatus: 2,
      appealRulings: 
       [ { ruling: 1,
           voteCounter: [[2, 1]],
           ruledAt: 1520241087000,
           deadline: 1520241090000 } ],
      appealJuror: [ { fee: 0.1, draws: [1, 2], canRule: false } ],
      description: 'test description',
      email: 'test@kleros.io',
      evidence: 
       [ { name: 'test name',
           description: 'test description',
           url: 'http://test.com',
           submittedAt: 1520241074602,
           _id: '5a9d09b2956bef0fbd75539e',
           submitter: '0xccc6366dc9da1362da4844372ac2ad849cd7f3f2' } ],
      netPNK: 20000000000000000,
      appealCreatedAt: [ 1520241071000 ],
      appealRuledAt: [ 1520241087000 ],
      appealDeadlines: [ 1520241090000 ]
}

[satello]

closes #93 and #81 (canRule comes directly from the chain)

[coveralls]

Pull Request Test Coverage Report for Build 468

• 88 of 90 (97.78%) changed or added relevant lines in 5 files are covered.
• 5 unchanged lines in 1 file lost coverage.
• Overall coverage increased (+1.9%) to 70.266%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/abstractWrappers/Disputes.js	78	80	97.5%

Files with Coverage Reduction	New Missed Lines	%
src/abstractWrappers/Notifications.js	5	71.79%

Totals
Change from base Build 462:	1.9%
Covered Lines:	622
Relevant Lines:	806

---

💛 - Coveralls

[epiqueras]

Closes #80