Update OmniSharp packages to latest build: v1.9-beta20

Author: DustinCampbell

package.json

@@ -105,7 +105,7 @@
     },
     {
       "description": "OmniSharp (.NET 4.6 / x86)",
-      "url": "https://omnisharpdownload.blob.core.windows.net/ext/omnisharp-win-x86-1.9-beta19.zip",
+      "url": "https://omnisharpdownload.blob.core.windows.net/ext/omnisharp-win-x86-1.9-beta20.zip",
       "installPath": "./bin/omnisharp",
       "platforms": [
         "win32"
@@ -116,7 +116,7 @@
     },
     {
       "description": "OmniSharp (.NET 4.6 / x64)",
-      "url": "https://omnisharpdownload.blob.core.windows.net/ext/omnisharp-win-x64-1.9-beta19.zip",
+      "url": "https://omnisharpdownload.blob.core.windows.net/ext/omnisharp-win-x64-1.9-beta20.zip",
       "installPath": "./bin/omnisharp",
       "platforms": [
         "win32"
@@ -127,7 +127,7 @@
     },
     {
       "description": "OmniSharp (Mono 4.6)",
-      "url": "https://omnisharpdownload.blob.core.windows.net/ext/omnisharp-mono-1.9-beta19.zip",
+      "url": "https://omnisharpdownload.blob.core.windows.net/ext/omnisharp-mono-1.9-beta20.zip",
       "installPath": "./bin/omnisharp",
       "platforms": [
         "darwin",