tests: use filepaths directly

After a long IRC discussion, it was decided that the use of direct
filepaths instead of the module is a more pure form of testing ,
although it may provide less overall coverage than the mixed integration
style imports used previously.

This will need to be remedied by further integration testing in
/test/integration.

test/script.js

@@ -1,9 +1,9 @@
 var assert = require('assert')
-var crypto = require('..').crypto
-var networks = require('..').networks
+var crypto = require('../src/crypto')
+var networks = require('../src/networks')
 
-var Address = require('..').Address
-var Script = require('..').Script
+var Address = require('../src/address')
+var Script = require('../src/script')
 
 var fixtures = require('./fixtures/script')