Add support for boot 2.0 and up

Boot's built-in repl task adds a fake.class.path System property which
refers back to the original user files (as opposed to the temporary
files it uses to actually do builds). We should prefer that to anything
else when the property is set.

Fixes #194.

autoload/fireplace/nrepl.vim

@@ -38,7 +38,17 @@ function! fireplace#nrepl#for(transport) abort
         \ client.describe.versions.nrepl.minor < 2
     throw 'nREPL: 0.2.0 or higher required'
   endif
-  if client.has_op('classpath')
+  " Handle boot, which sets a fake.class.path entry
+  let response = client.process({'op': 'eval', 'code':
+        \ '[(System/getProperty "path.separator") (System/getProperty "fake.class.path")]', 'session': ''})
+  let cpath = response.value[-1][5:-2]
+  if cpath !=# 'nil'
+    let cpath = eval(cpath)
+    if !empty(cpath)
+      let client._path = split(cpath, response.value[-1][2])
+    endif
+  endif
+  if !has_key(client, '_path') && client.has_op('classpath')
     let response = client.message({'op': 'classpath'})[0]
     if type(get(response, 'classpath')) == type([])
       let client._path = response.classpath