Use line ending length for mapping positions/characters

Previously the line ending length was hard-coded to one which
would cause TextBuffer.scanInRange() to return incorrect results
since one character per line wasn't being accounted for.

Closes #428

spec/app/text-buffer-spec.coffee

@@ -725,6 +725,13 @@ describe 'Buffer', ->
       expect(buffer.characterIndexForPosition([2, 0])).toBe 61
       expect(buffer.characterIndexForPosition([12, 2])).toBe 408
 
+    describe "when the buffer contains crlf line endings", ->
+      it "returns the total number of characters that precede the given position", ->
+        buffer.setText("line1\r\nline2\nline3\r\nline4")
+        expect(buffer.characterIndexForPosition([1])).toBe 7
+        expect(buffer.characterIndexForPosition([2])).toBe 13
+        expect(buffer.characterIndexForPosition([3])).toBe 20
+
   describe ".positionForCharacterIndex(position)", ->
     it "returns the position based on character index", ->
       expect(buffer.positionForCharacterIndex(0)).toEqual [0, 0]
@@ -734,6 +741,13 @@ describe 'Buffer', ->
       expect(buffer.positionForCharacterIndex(61)).toEqual [2, 0]
       expect(buffer.positionForCharacterIndex(408)).toEqual [12, 2]
 
+    describe "when the buffer contains crlf line endings", ->
+      it "returns the position based on character index", ->
+        buffer.setText("line1\r\nline2\nline3\r\nline4")
+        expect(buffer.positionForCharacterIndex(7)).toEqual [1, 0]
+        expect(buffer.positionForCharacterIndex(13)).toEqual [2, 0]
+        expect(buffer.positionForCharacterIndex(20)).toEqual [3, 0]
+
   describe "markers", ->
     describe "marker creation", ->
       it "allows markers to be created with ranges and positions", ->

src/app/text-buffer.coffee

@@ -145,6 +145,9 @@ class Buffer
   lineLengthForRow: (row) ->
     @lines[row].length
 
+  lineEndingLengthForRow: (row) ->
+    (@lineEndingForRow(row) ? '').length
+
   rangeForRow: (row, { includeNewline } = {}) ->
     if includeNewline and row < @getLastRow()
       new Range([row, 0], [row + 1, 0])
@@ -168,12 +171,13 @@ class Buffer
     position = Point.fromObject(position)
 
     index = 0
-    index += @lineLengthForRow(row) + 1 for row in [0...position.row]
+    for row in [0...position.row]
+      index += @lineLengthForRow(row) + Math.max(@lineEndingLengthForRow(row), 1)
     index + position.column
 
   positionForCharacterIndex: (index) ->
     row = 0
-    while index >= (lineLength = @lineLengthForRow(row) + 1)
+    while index >= (lineLength = @lineLengthForRow(row) + Math.max(@lineEndingLengthForRow(row), 1))
       index -= lineLength
       row++
 
@@ -358,7 +362,7 @@ class Buffer
     @scanInRange(regex, @getRange(), iterator)
 
   scanInRange: (regex, range, iterator, reverse=false) ->
-    range = Range.fromObject(range)
+    range = @clipRange(range)
     global = regex.global
     flags = "gm"
     flags += "i" if regex.ignoreCase