fix(lib): handle the case where opts is undefined

when using contentful-export as a library opts object will be undefined and will cause a crash at
the content-batch-libs when creating the client also the promise was not resolving to the reponse
when it is used as library

closes #3

Author: Khaledgarbaya

.gitignore

@@ -5,3 +5,4 @@ coverage
 node_modules
 config.json
 dist
+*.swp

lib/run-contentful-export.js

@@ -8,22 +8,32 @@ var log = require('npmlog')
 
 Promise.promisifyAll(fs)
 export default function runContentfulExport (usageParams) {
-  const {opts, errorLogFile} = usageParams
+  let {opts, errorLogFile} = usageParams
+  let exportToFile = true
+  if (!opts) {
+    exportToFile = false
+    opts = {}
+    opts.sourceSpace = opts.sourceSpace || usageParams.spaceId
+    opts.sourceManagementToken = opts.sourceManagementToken || usageParams.managementToken
+  }
   const clients = createClients(opts)
   return getFullSourceSpace({
     managementClient: clients.source.management,
     spaceId: clients.source.spaceId
   })
-  .then((response) => {
-    const responseFile = `${opts.exportDir}/contentful-export-${clients.source.spaceId}-${Date.now()}.json`
-    log.info('Writing the data to a json to file at : ' + responseFile)
-    return fs.writeFile(responseFile, jsonStringifySafe(response))
-  })
-  .catch((err) => {
-    dumpErrorBuffer({
-      sourceSpace: opts.sourceSpace,
-      errorLogFile: errorLogFile
+    .then((response) => {
+      if (exportToFile) {
+        const responseFile = `${opts.exportDir}/contentful-export-${clients.source.spaceId}-${Date.now()}.json`
+        log.info('Writing the data to a json to file at : ' + responseFile)
+        return fs.writeFile(responseFile, jsonStringifySafe(response))
+      }
+      return response
+    })
+    .catch((err) => {
+      dumpErrorBuffer({
+        sourceSpace: opts.sourceSpace,
+        errorLogFile: errorLogFile
+      })
+      throw err
     })
-    throw err
-  })
 }