Preprocessor outputs one sentence per line

Rather than having each word/tag tuple on a line, now each sentence is on a single line
A few errors slip by and are printed on new lines, but it shouldn't be a big issue

Also added preprocessor to makefile, syntax is:
	`make pre OUT=data/convert NUM=4`
`OUT` is the output directory and `NUM` is the number of merged output files you want (I don't know a better way of doing this other than using variables)

Example:

```
$ make pre OUT=data/convert NUM=4
$ wc -l data/convert/*.pos
   11501 data/convert/section_0.pos
   11506 data/convert/section_1.pos
   11481 data/convert/section_2.pos
   11432 data/convert/section_3.pos
   45920 total
```